Blueberry French Custard Cake

French Custard Cake is a creamy and indulgent dessert with juicy blueberries and refreshing lemon zest layered on a Biscoff cookie crust. The cake is served topped with lemon mascarpone frosting and homemade blueberry sauce.

Just the name of this will tell you how luscious this dessert will be. A French custard cake with blueberries that just burst in your mouth with flavor on top of a cookie crust made from Biscoff cookies with melted butter. Then, it is topped off with a dreamy layer of buttercream mascarpone frosting. But that is not all. The blueberry sauce comes next, full of fresh blueberries with a touch of vanilla extract to boost its flavor. You expect to find this cake at a fancy restaurant or bakery.

This Blueberry French Custard Cake is perfection. I went ahead and topped it with some lemon mascarpone buttercream and homemade blueberry sauce. The buttercream is so perfect here, its like another creamy layer, but so different in texture from the custard. Also, it adds another decadent level of texture and fresh flavor. You can totally skip the buttercream if you want to keep the cake a little lighter. However, make sure you top it with that homemade blueberry sauce!

You may be able to get this decadent dessert at a restaurant, but also you can so easily make it yourself without having to leave your house. When you look at this cake and the long list of ingredients, you may think it is too complicated, or there is too much to do. But this is easy to do, or I would not be asking you to do it. You are just making a custard cake on a cookie crust and covering it with some mascarpone frosting and blueberry sauce.

The custard cake is so simple and made with pure, wholesome ingredients like cream, butter, flour, and vanilla. It will only take you a few minutes to make it, and then you have to let it chill for an hour. The crust is also easy. Mix the crumbs with butter and push it into the crust, bake it, and then you are done until the custard is ready. Then, combine it and bake it while you finish the frosting and sauce.

I love making delicious cakes, since they are very popular on the blog I recommend you try this Strawberry Poke Cake, German Chocolate Poke Cake and Baileys Poke Cake.

Why you will love this recipe

• A decadent dish that is easy to make: You can show off what you made.
• Fresh wholesome ingredients: When you make it yourself, you know what is in it.
• It is inexpensive: No reason to pay so much for something you can make.
• You can stay home: Why bother going out when you can stay in?

What you’ll need to make blueberry french custard cake

I wanted the cake to taste very fresh, the custard itself doesn’t feel heavy, since its made with just a little flour and few eggs, its very creamy and light. I added some lemon zest for some summery brightness and freshness and also 2 cups of blueberries. Every delicious bite of this creamy goodness is followed by a tart burst of juicy blueberries. Similarly, a subtle lemon flavor and a delicious caramelized crumble from the biscoff crust.

Special items:

• Small saucepan – For heating the cream.
• Large saucepan – To make the blueberry sauce.
• Food processor – For grinding the cookies.
• Stand mixer – To make the frosting.
• Springform pan – 10-inch springform cake pan.
• Mixing bowls
• Cooking utensils

Ingredients:

For the custard:

• Heavy cream – I use heavy cream because it makes my custard rich and thick.
• Butter – Softened butter for added creaminess.
• Vanilla extract – Do not use vanilla flavoring. Make sure it is real vanilla.
• All-purpose flour – I use all-purpose white flour.
• Caster sugar – This is a superfine sugar that dissolves better for making custard and other silky baked goods.
• Eggs – Two whole large eggs plus two large egg yolks. You can save the egg whites for other recipes. See my Expert Tip section.
• Lemon zest – I recommend you zest your own lemon for the best taste. It only takes a few minutes, and it is very easy to do.
• Blueberries: If fresh blueberries are not available, you can use frozen.

For the crust:

• Biscoff cookie crumbs – These cookies have a unique flavor with a crunchy taste that stands out from the others.
• Unsalted butter – Melted and unsalted for mixing with the crumbs to make the crust.
• Granulated sugar – Perfect for the texture and sweetness of this crust.

For the blueberry sauce:

• Blueberries – Fresh is best but frozen will work in a pinch.
• White granulated sugar – Great for the sauce. No need for special sugar here.
• Vanilla extract – As before, use the real stuff for the best flavor.
• Cornstarch slurry – Mix one tablespoon of cornstarch with one tablespoon of cold water for thickening.

For the buttercream:

• Butter – You will need one whole stick of softened butter.
• Mascarpone cheese – Should be chilled for this recipe.
• Powdered sugar – For easier dissolving.
• Lemon zest – Once again, it is better to do it yourself.
• Salt

How to make blueberry french custard cake?

1. Prepare the pot: First whisk the eggs, egg yolks, sugar, lemon zest, salt, and flour in a large bowl and then set it aside.
2. Heating the custard: Now, heat the heavy cream in a small saucepan on medium heat until it starts to boil. Then, please remove it from the heat and stir in the vanilla extract.
3. Mixing the custard: Slowly, pour about one-third of the heavy cream into the egg mixture, whisking constantly. DO NOT add all the cream at once. The heat will cook the eggs. After stirring, slowly add half of the cream’s left. Whisk for 30 seconds before gradually adding the rest of the heavy cream and butter, continuing to whisk.
4. Cool: Cover with plastic and let it cool on the counter for 20 minutes before chilling it into the fridge for one hour.
5. Make the crust: To make the crust, first, preheat the oven to 350 degrees F. Then, grind the Biscoff cookies in a food processor until you have three cups of crumbs. Then, mix the crumbs, butter, and sugar in a medium bowl with a rubber spatula until it is combined.
6. Press: Next, press the crumbs into the bottom and slightly up the sides of a 10-inch springform pan. Ensure it is very compact and tight, so the custard does not leak out. Pre-bake for seven minutes before adding the custard.
7. Cook the custard: After it is cool, butter the edges of the pan and layer the blueberries on top of the crust. Then, pour the chilled custard into the pan and bake for 50 minutes, until golden brown. Remove and put it on a wire rack to cool completely.
8. Make the blueberry sauce: While the cake is cooking, mix blueberries, sugar, and water in a large saucepan over medium heat. Please bring it to a low boil, stirring frequently, but be careful not to crush the berries. In a small bowl, make the cornstarch slurry and then pour it into the blueberry mixture. Continue to simmer for about 10 minutes or until it coats the back of a spoon. Set it aside to cool completely before topping the cake.
9. Make the mascarpone buttercream: In the meantime, put the softened mascarpone and butter in an electric stand mixer fitted with a wire attachment and cream for two minutes on medium until smooth. Then, add sugar, lemon zest, and salt, until well incorporated. If it is too thick, add cream one tablespoon at a time.
10. Frost and serve: Once the cake is completely cool, frost with the buttercream and then pour the blueberry sauce on top before serving.

Expert tip

What to do with extra egg whites

First, egg whites will stay fresh in the fridge for three days in an airtight container or in the freezer for several months. Try freezing them in an ice cube tray and storing them in a freezer bag for easier storage. Then, thaw them out as needed. You can use these for omelets and soups such as egg ribbon soup, Chinese chicken corn soup, or hot and sour soup. They are also great for pavlova or almond cookies.

You can also use egg whites to make granola, meringue, icing, glaze for bread, donuts, or mousse. They are great for making souffles, angel food cakes, mayo, cocktails, and English muffins. You can even scramble them up and eat them on their own. Coconut macaroons are made with egg whites and baked Alaska and nougat. You can do so many things with egg whites in the kitchen that you may forget that they are good for other things.

You can rub them into your skin to clean and tighten pores as well as firm things up to get rid of wrinkles. Not only that, but it contains vitamin A, E, biotin, and folate, so it helps repair your damaged hair too. Go ahead and take a shower with those egg whites. You can use them as soap and shampoo. No reason to waste them! They build a stronger cortex and smoother cuticle for longer, shinier hair.

Recipe variations and add-ins:

• Other fruit: If you cannot find blueberries, you can substitute them for raspberries, blackberries, or strawberries.
• Different crust: The crust can be changed to a graham cracker or some other kind of cookie if you like. I have tried it with Nilla Wafers, and it was a hit with my family. 
• Other frosting: This rich cake would also be good with another kind of frosting instead of mascarpone.
• Lighter topping: For something lighter, top it with whipped cream. I have my own homemade recipe for whipped cream that you can make.
• Other citrus: Blueberry would also be sensational with orange or lime instead of lemon.

Serving suggestions:

This is a rich and creamy dessert for any celebration or meal. Here are some other ideas.

• Serve it for a summer barbecue with burgers and some blueberry margaritas.
• Pan-seared salmon with blueberries would also be a nice entrée to have with this cake for dessert.
• This blueberry French custard cake also tastes incredible, served by itself as a frozen dessert. Not all the way frozen. Just chill for about an hour and serve in a bowl with a drizzle of warm caramel sauce. 
• Instead of ice cream, serve this delicious custard cake with my strawberry sorbet. It is easy to make, and you do not need an ice cream machine.
• For a romantic dessert for two, serve this with a bottle of Rose champagne or sparkling wine. They pair well with blueberries. 

Frequently asked questions

What is the difference between custard and pudding?

They are both thick, sweet, creamy desserts, but custard is much smoother and firmer, with a thicker and more gelatinous texture. The eggs in the custard cause the protein to thicken when heated, while pudding is thickened by cornstarch or tapioca and does not necessarily need eggs. There are three kinds of custard: baked, stirred, and frozen. This recipe is made with baked custard, which is particularly rich, creamy, and smooth.

Why won’t my French custard cake set?

In order for custard to set, your egg yolks have to be cooked to a little less than 212 degrees F to kill the alpha-amylase enzymes so they do not eat all the starches needed. It may look thick at first but as the enzymes left over start eating the starch, your custard will soon turn watery. It would be best if you continued to cook your custard for two minutes after the bubbles started appearing, stirring constantly. However, to fix this problem, you can reboil your custard to kill those enzymes or add some cornstarch slurry to the custard to make it thicker.

What happens if custard gets too hot?

Now that you know what underheated custard can do, you need to know what overheated custard does. When your custard is cooked too long or at a temperature higher than it needs, the proteins in the egg will coagulate and stick to each other. This causes clumps and curdling, which is never good. Once you have too many bonds in your custard, it can be hard to break it up, and you may have to start over with new eggs. It can also break down the protein and cause an eggy flavor that you will not like.

What is the difference between caster and granulated sugar?

Some say that caster sugar (also known as extra fine sugar) is a better choice than granulated sugar in delicate recipes like custard because it dissolves faster. It has a softer texture, so it is easier to mix into creamy ingredients. But if you want to make this recipe and you only have granulated sugar, there is no reason to run to the store. Just add it to a food processor and grind it for a few seconds. Then, run it through a fine strainer before adding it to your recipe. 

How to store leftovers:

• Refrigerate: Refrigerate custard cake in an airtight container for up to five days. 
• Freezing: Freezing is not recommended. 

Recipe tips:

• Do not add all the cream to the egg mixture when making the custard. The heat will cause the eggs to cook.
• You can use a high-powered blender to grind the cookies if you do not have a food processor.
• You could also put the cookies in a zipper baggie and smash them with a rolling pin or can of vegetables. But make sure you get them super fine. You do not want your custard to leak.
• Instead of egg whites, you can use applesauce, flaxseeds, or soaked chia seeds.
• Caster sugar is a fine sugar that dissolves better. If you do not have any, you can make your own out of granulated sugar by running it through the food processor.