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Chocolate custard cake

January 13, 2023  Chef Austin Avatar
Chocolate custard cake

Slice of Chocolate custard cake on a plate

Whether you consider this a giant chocolate tart or chocolate custard cake, we will agree it’s one of the most delicious desserts you will ever make. A cross between a chocolate mousse cake and a chocolate Flan Patissier, it’s deeply chocolatey, ultra creamy, yet not overly rich, and shockingly straightforward to make. The perfect finale for any occasion!

Slice of Chocolate custard cake on a plate

Look at all that creamy chocolate custard! How can this not get you excited???!

Chocolate custard cake

I feel like I don’t need to say much about this cake because the photos and recipe video do all the talking for me.

It’s as chocolatey and creamy as it looks. You can cut it into neat slices (like… cake!). But when you eat it, it’s gloriously creamy.

It’s luxurious, with a rich mouthfeel. It is a real custard, after all, nothing like the fake stuff sold in cartons at the store which is a sad imitation of the real deal.

But this is not overly rich and definitely not overly sweet.

Decadent enough for special occasions, easy enough to make for a morning tea at work.

Wait a sec. Did I just convince myself this is the perfect cake for any occasion??? 😂

Dusting a Chocolate custard cake decorated with raspberries with icing sugar

This chocolate custard cake is an invention that started out as a chocolate version of a Blueberry custard cake I shared a few months ago, a recipe where custard is baked on top of a vanilla sponge layer.

Numerous attempts later, I gave up but out of the fails came this glorious chocolate custard cake that is probably one of my best baking inventions ever. Big call – but I’m standing by it!

Also – proof of creaminess:

Creamy inside of a slice of Chocolate custard cake
Stopped in the middle of hoovering down this cake so I could show you how creamy the custard is.

What you need

Here’s what you need to make this Chocolate custard cake.

1. Chocolate custard

This cake is made using crème pâtissière, a creamy custard that is used in many French desserts. The recipe I’m using today is based on the custard used in the famous (giant!) French vanilla custard tart, Flan Pâtissier, with chocolate added.

While exact recipes for crème pâtissière vary depending on the intended use (ie. baked vs not baked; required viscosity for pouring vs piping vs filling vs spreading, flavourings added etc), the base ingredients are almost always the same:

How to make Chocolate custard cake
  • Egg yolks – for richness and also to help set the custard.

    Leftover egg whitesHere’s my list of what I do with them and all my egg white recipes can be found in this recipe collection.

  • Cornflour/cornstarch – For setting the custard and making it shiny (regular flour makes it dull). Attention FRENCH READERS: Do not use yellow cornflour, use white cornstarch!

  • Sugar – It’s best to use caster sugar / superfine sugar as the grains are finer than regular / granulated sugar so it dissolves more easily.

    Note: This chocolate custard cake is not excessively sweet! One of the things I adore about French desserts is that they are far less sweet than other typical Western desserts. It suits my palette as I grew up eating Japanese baked goods which is heavily influenced by French pastry.

  • Milk – The liquid for custard. Some recipes also use cream, for added richness. I don’t feel it’s needed in this recipe. The chocolate makes it rich enough!

  • 70% cocoa chocolate – This cake needs to be made using 70% cocoa chocolate to ensure the custard sets to the right consistency and good chocolate flavour. Lower cocoa % (eg milk chocolate, usually around 30% cocoa) = softer chocolate & less chocolate flavour = custard sets softer, is paler and chocolate flavour is not as strong. I found this to be the result when I tried this with regular dark chocolate chips (45% cocoa).

    Better quality = better result! I use Lindt 70% cocoa dark chocolate which is actually an eating chocolate, and a good quality one at that. It’s better quality than the 70% chocolate sold in the baking aisle, so I always stock up whenever I see it on sale!

  • Vanilla extract – For background flavour. When making a vanilla crème pâtissière (such as with Flan Pâtissier) or a vanilla pouring custard where vanilla is the forward flavour, I will usually recommend using vanilla beans or vanilla bean paste for better flavour. Plus, let’s just say it, people are always impressed when they see the little black specks. You used real vanilla in this, wow! 😇

    Today, chocolate is our primary flavour so there’s no need to indulge in “real vanilla”. Vanilla extract will do nicely. Not vanilla essence please, that tastes like what it is – artificial vanilla flavour.

Oreos are a great shortcut for a cookie base that’s got intense chocolate flavour and colour, with the bonus that the cream filling helps the crust hold together.

Other bases I tried for this cake: chocolate pâte sucrée (French tart crust) and various versions chocolate sponge (this didn’t work, testing notes at the bottom of the post) and this Oreo biscuit base. I preferred the biscuit base because it’s a relatively thin layer which provides the necessary structure but doesn’t detract from the star of the show – the chocolate custard. It’s also a nice textural contrast with the bonus that it’s the easiest to make!

How to make Chocolate custard cake

How to make chocolate custard cake

This section has step photos and talks through the why for key parts of the recipe. There’s also the recipe video above the recipe card, though if you’re a baking pro you might just want to skip straight down to the recipe!

1. Preparing the cake pan

Cakes, tarts etc made with crushed up biscuits (like cheesecakes) need to be made in pans with a loose base so you can remove the finished cake. You can’t flip it upside down like a sponge cake because the base will crack and the surface will be ruined!

So for today’s recipe, you will need a springform pan with removable sides. Because the base of springform pans have a lip, it’s best to use it upside down so the finished cake slides off it easily. Insurance policy to ensure the base doesn’t crack!

How to make Chocolate custard cake
  1. Flip base upside down.

  2. Grease the base with butter then stick a square-ish sheet of baking paper on it (parchment paper).

  3. Clip the sides in place and leave the excess paper sticking out the sides (handy to grip when removing the finished cake).

    Clipping the sides onto the inverted base can be a bit fiddly. I find the easiest way is to pop a folded tea towel under the base so it’s slightly elevated off the work surface, then clip the sides in.

  4. Lightly grease the sides with butter then line with baking paper.

* If you are a pastry master and have an entremet ring, you can skip this step. But you already know this! 😇


2. Making the chocolate custard

Please – resist the urge to eat all the custard out of the pot. Save a little for the cake!

Short form – how to make chocolate custard

Heat milk with half sugar. Whisk yolks and remaining sugar, then cornflour. Temper eggs, thicken on stove, whisk 45 seconds after bubbles appear. Stir in chocolate. Done!

How to make Chocolate custard cake
  1. Heat milk with vanilla and about half the sugar until just before boiling. You can just eyeball the amount of sugar that goes in.

  2. Whisk the egg yolks, remaining sugar and cornflour/cornstarch in a separate large bowl.

  3. Whisk in milk – Slowly pour the hot milk in while whisking constantly, which will ensure the hot milk doesn’t cook the eggs. Pour all the milk in and whisk until combined.

    This step by which hot liquid is poured in a controlled manner into cold eggs without causing them to cook is called tempering eggs.

    Precaution step: If the saucepan is a little heavy for you, just use a jug or ladle to assist. Once you get about 1 cup of of the milk whisked in, you don’t need to worry about scrambling the eggs!

  4. Transfer the egg-milk mixture back into the saucepan. Now we’re going to cook it for a few minutes until it thickens into a custard.

How to make Chocolate custard cake
  1. Thicken custard – Pour the egg-milk mixture back into the same saucepan. Place over medium low heat, whisking constantly so the base doesn’t catch, until it starts to thicken (you will feel it). It should happen within 3 to 5 minutes. If it gets lumpy, remove off heat, whisk vigorously – will become smooth.

  2. Lazy bubbles – The sight of lazy bubbles is the trigger that determines the right cook time for custard. They will start to appear once the custard is thickened, and it’s hot and steamy. You’ll need to pause stirring for a few seconds to see if they appear.

  3. Stir 45 sec – Once you see the bubbles, whisk constantly on the stove for a further 45 seconds then remove from stove. The rule for making French custard is 30 seconds for every 500ml/2 cups of milk. That is, for every 2 cups of milk used in the custard, stir for 30 seconds after the bubbles start appearing. Because we are using 3 cups of milk, we stir for 45 seconds.

  4. Add chocolate – Remove from the stove, add chocolate and stir until fully melted. See below for what it looks like!

How to make Chocolate custard cake
  1. Thickness – The custard should be thick enough such that it mounds slightly on the surface, like pictured above.

  2. Set aside – Transfer into a bowl, immediately cover with cling wrap touching the surface to prevent a skin from forming. If you can see lumps in your custard, feel free to strain through a fine mesh.

    Then set the custard aside while preparing the base. There’s no need to rest chocolate custard overnight, like we do with the vanilla custard for Flan Pâtissier. Reason: Vanilla custard is more delicate and benefits from overnight flavour development. Chocolate custard doesn’t need it.

    Make-ahead option – If you want to get ahead, the custard can be refrigerated overnight then used the next day.


Blitz and press. Nice and easy! No food processor? No worries! Just bash the cookies in a ziplock bag using a rolling pin or something heavy.

How to make Chocolate custard cake
  1. Cookies – Break up the cookies with your hands and place in a food processor.

  2. Blitz until they become fine crumbs. Add melted butter, then blitz again until combined.

  3. Transfer crumbs into prepared pan.

  4. Press evenly and firmly on to the base. I spread the crumbs with a spatula then use the underside of a straight-sided, flat-bottomed measuring cup to press them flat. But honestly, even your hands will do the job!


4. Baking

Home stretch!

How to make Chocolate custard cake
  1. Whisk custard until smooth. It firms up as it cools but should still be warm by the time you get to using it. Though you can, as noted above, leave the custard overnight and finish the cake tomorrow.

  2. Pour the custard into the prepared cake pan.

  3. Spread the custard and smooth the surface. No need to be too meticulous here as the custard will thin as it heats up and spread out evenly.

  4. Bake for 1 hour at 180°C/350°F (160°C fan-forced), rotating the cake at the 45 minute mark. The cake will puff up towards the end and a thin (chocolatey!) skin will form on the surface. This is a signature characteristic of Flan Pâtissier (French Custard Tart) on which this recipe is based!

Overhead photo of freshly baked Chocolate custard cake
  1. Cool overnight – Remove the cake from the oven and leave to cool on the counter for at least 3 hours. Don’t be alarmed if it deflates – that is what is supposed to happen!

    Then refrigerate for at least 12 hours, or even longer.

    If there is any hint of warmth in the cake when you put it in the fridge, do not cover the cake with cling wrap as it will make it sweat. Because of the type of cake this is, there is no risk of it drying out so just leave it uncovered.

  2. Remove the sides of the springform pan then slide the cake off the base (and feel smug at how easy it is because you learnt the inverted cake base trick!). Now, it’s ready for serving…… I mean, YAY, it’s time to EAT!!!

Overhead photo of Chocolate custard cake

More matters of chocolate custard cake

Decorating

Raspberries or sliced strawberries look lovely on chocolate desserts, as does a dusting of icing sugar (powdered sugar), as pictured in post. A dollop of Chantilly cream (lightly sweetened vanilla cream) or mascarpone wouldn’t go astray either, or a scoop of vanilla ice cream!

Serving

I like to cut the cake while fridge cold, for neat smear-free slices, then leave it out for around 30 minutes to bring to room temperature before serving for the creamiest mouthfeel. Having said that though, on hot summer days, cold custard cake is DIVINE!

Storage

I had to label a slice with an aggressive “DO NOT TOUCH!!!” sign to protect it from vultures to check the shelf life! It was perfect for 48 hours after removing from the cake pan, then still good on day 5 though the biscuit base was noticeably softer.

I forgot to try but I doubt it will freeze. Custards typically don’t freeze well.

Close up photo of a slice of Chocolate custard cake

And there you have it! A chocolate custard cake. I suppose some would argue that it’s a chocolate tart, and being that it is actually a chocolate version of the French custard tart, Flan Pâtissier.

But with a layer of custard that thick, to me it looks more like a chocolate mousse cake than a tart.

The name might be open to debate, but the delicious is not! I hope you give it a go one day! – Nagi x


Watch how to make it

Slice of Chocolate custard cake on a plate

Print

Chocolate Custard Cake

Recipe video above. Whether you consider this a giant chocolate tart or chocolate custard cake, we will agree it’s one of the most delicious desserts you will ever make. A cross between a chocolate mousse cake and a chocolate Flan Patissier (French custard tart), it’s deeply chocolatey, ultra creamy, yet not overly rich, and shockingly straightforward to make. The perfect finale for any occasion!
Course Dessert
Cuisine Western
Keyword Chocolate custard cake, chocolate custard tart, chocolate flan patissier, chocolate mousse cake
Prep Time 30 minutes
Cook Time 1 hour
Cooling 15 hours
Servings 10 – 12 people
Author Nagi

Ingredients

BASE:

  • 200g/ 7oz Oreo cookies (1.5 standard packs, Note 1)
  • 60g/ 4 tbsp unsalted butter , melted

CUSTARD:

  • 3 cups milk , full fat
  • 2 tsp vanilla
  • 2/3 cups caster sugar (superfine sugar, sub regular)
  • 120g/ 4.2 oz egg yolks (~6 – 7 large eggs, Note 2)
  • 5 tbsp (50g) cornflour / cornstarch
  • 200g / 7 oz 70% cocoa chocolate , finely chopped (I use Lindt, Note 3)

FOR SERVING (optional):

  • Chantilly cream
  • Raspberry or strawberries
  • Icing sugar / powdered sugar , for dusting

Instructions

PREPARATION:

  • Prepare pan: Flip the base of a 20cm / 8″ springform pan upside down – this makes it easier to remove the finished cake without the lip in the way. Grease pan base with butter, then press on a square sheet of baking paper. Clip the pan sides onto the base, letting the excess paper stick out (ease of removal later).
  • Preheat oven to 180°C / 350°F (160°C fan-forced).

CUSTARD:

  • Heat the milk, vanilla and about half the sugar in a large saucepan over medium high heat until just before boiling, stirring to dissolve the sugar.
  • Yolk mixture: Place egg yolks and remaining sugar in a large bowl and whisk to combine. Add cornflour and whisk until smooth.
  • Temper eggs: While whisking the eggs, slowly pour in the hot milk in a thin stream while whisking. Whisk until fully combined.
  • Thicken custard: Pour the egg-milk mixture back into the same saucepan. Place over medium low heat, stirring constantly so the base doesn’t catch, until it starts to thicken (you will feel it). It should happen within 3 to 5 minutes. If it gets lumpy, remove off heat, whisk vigorously – will become smooth.
  • Stir 45 sec after bubbles: When the custard is thickened and steamy, and you see the first big lazy bubbles appear on the base (pause whisking to see), whisk constantly on the stove for a further 45 seconds then remove from stove.
  • Add chocolate and stir until fully melted.
  • Cool: Transfer into a bowl, immediately cover with cling wrap touching the surface. (You can strain if you’re concerned about lumps). Set aside while preparing the base.

BISCUIT BASE:

  • Blitz cookies: Roughly break up Oreos with hands and place in food processor. Blitz until they become fine crumbs. Add melted butter, then blitz again until combined.
  • Press: Transfer crumbs into prepared pan, pressing evenly and firmly on to the base (I use the underside of a straight-sided, flat-bottomed cup measure to do this).

BAKE:

  • Bake 1 hour: Whisk custard until smooth to loosen. Pour onto the base, smooth surface. Bake 60 minutes, rotating the cake pan at the 45 minute mark.
  • Cool for 3 hours on the counter, in the pan. Refrigerate at least 12 hours.
  • Serve: Best to cut when fridge cold and serve at room temp (for creamiest custard!). Remove springform sides and paper, then use paper overhang to slide the cake off the base. Cut like cake and serve! Lovely with dollop of Chantilly cream and a raspberry or strawberry. Dust with icing sugar to make it pretty!

Notes

1. Oreo cookies – You can also use plain chocolate biscuits instead (ie without a filling), such as Arnott’s Chocolate Ripple, but add 1 1/2 tbsp / 20g of butter. This is because Oreo cookies have a filling which is partly what helps bond the crust.

2. Yolks – safest to weigh because egg and yolk sizes differ and this custard relies on egg to help it set. 120g / 4.2 oz yolks is 100ml / 3.4 oz, just shy of 1/2 cup. Usually 6 large eggs weighing ~55g / 2oz each (carton labelled “large eggs” because it’s an industry standard).

Leftover egg whitesHere’s my list of what I do with them and all my egg white recipes can be found in this recipe collection.

3. Chocolate – Must use 70% cocoa chocolate to ensure the custard sets to the right consistency and good chocolate flavour. Lower cocoa % (eg milk chocolate usually around 30%) = softer chocolate & less chocolate flavour = custard sets softer, is paler and chocolate flavour is not as strong.

Storage – At its best for the first 48 hours. Keeps for 5 days though the biscuit base does start to soften (it’s really not a big deal). Store in fridge.

Fellow custard-lovers. Unite!


Life of Dozer

No chocolate for you Dozer! How about some croissant instead? (Like I have a choice! 😂)

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