Boston Cream Cake … Soft and fluffy vanilla sponge cake, filled with custard cream in the middle, and frosted with more custard cream on top with the final layer of decadent chocolate ganache. How does that sounds to you? I don’t know about you, but this cake is a real treat inside and out, every crumbs counts.
There is something about custard that I love when used in pastries and desserts. The silky, smooth texture and the creamy taste is absolutely to die for. Second to chocolate ganache, I would say that this is my next favorite frosting, although technically it is not a frosting, but who cares? I custard pastry cream makes every bite of cake and pastry taste so good you wouldn’t be able to stop eating it. Think about custard cream on danishes, donut, pie tarts, or trifle or cake like this one. It completes the package of what a perfect cake or pie.
How to Make Boston Cream Cake
There are 3 major parts in making Boston Cream Cake which all can be made ahead of time, separately. The Cake, Custard Pastry Cream and Chocolate Ganache. Let us talk about this one by one.
The Vanilla Sponge Cake
The base cake is a light and airy vanilla sponge cake. It uses the method of separating the egg yolk and whipping the egg white to give the cake a lighter fuller cake. Key thing to remember when making this sponge cake
- Use room temperature eggs for easy creaming and whipping. Cold eggs will not cream better and will result to a dense cake.
- Use combination of all-purpose flour and cake flour: Cake flour is lighter and has the lowest protein content which largely affect the texture of the cake. Cake that uses cake flour have a lighter texture, and fine loose crumbs.
- Fold Gently: The creaming process of egg and sugar aims to trap air in the batter. Trapped air in the batter produces a light and airy cake. It is important to retain the trapped air, and so a gentle folding method is important when adding the whisked egg whites and flour to the cake batter. Fold slowly, and do it manually. Do not use a mixer to do it so you have more control.
The Vanilla Custard Filling
Boston Cream is not Boston cream without the custard filling. Custard Pastry Cream is basically egg, sugar, flour, milk and butter. This is one delicious versatile pastry cream that is so easy to make. Key things to remember:
- Use Whipping Cream: Do not use skin milk or non-dairy milk substitute. Although they will work, but they will not be as creamy.
- Do NOT Cook in High Heat: Cook the pastry cream slowly in low heat. You cannot rush the process, you need to be patient. Cooking the pastry cream in high heat could make the mixture separate, ending with a clumpy cream rather than a smooth cream. The process will take about 10 -12 minutes before you get to a thick, smooth consistency.
- Stir, Stir: Since pastry cream contains cornstarch and flour, you have to keep on stirring it to prevent lumps. Leave it even for just 1 minute and the mixture will be lumpy. If you end up with a lumpy cream, you can fix it by passing it through a sieve to remove the lumps. This is not necessary if you just cook in low heat and keep on stirring.
- Chill: Pastry cream needs to be cooled down and chilled to allow it to further thicken. Thick pastry cream is more important if you are using it as a filling or for spreading on top.
The Chocolate Ganache
Well, we reach the final part which is making the Chocolate Ganache. This is a chocolate frosting made with melted chocolate and whipping cream. Just to simple ingredients, simple and easy to make. We are going for a medium consistency here, the one the you can pour or spread on top easily. This will go on top of the custard, so it is important to have the consistency just right. If you make it too thick, it will mix with the custard when you spread it on top. I used about 1/2 cup melted chocolate for this cake. Key things to remember when making Chocolate Ganache:
- Use a Good Quality Chocolate: There is only 2 ingredients in making chocolate ganache, so make sure to use a good quality chocolate. Spending few pennies goes a long way.
The Whipped Cream
Totally optional, but highly recommended. It is an extra step, but a step that is totally worth it. I wouldn’t do it any other way. The small amount of whipped cream brings all the components together, a wonderful harmony between the vanilla sponge cake, pastry cream and chocolate ganache. Making whipped cream is so easy, keep this few point in mind:
- Use cold cream – Cream has to be cold to whip. If it is not cold from the fridge it is very hard to get it to whip to stiff peaks. This is key to having a soft, fluffy whipped cream that hold its shape longer.
- Chill the bowl and the whip – Chill your bowl and the whip in the freezer before using it, at least 15 minutes. This will help the cream to stay cold during whipping process, and will produce a stiff and stable whipped frosting that can be used for piping and decorating. A warm bowl and whip can hinder in making a fluffy whipped cream.
- Under whip rather than over whip – It’s better to under whip than over whip. Over whipping the cream will end you up with a butter and you don’t want that to happen. You have over whipped it if the consistency becomes too thick and it resembles a lump of thick cloud, also you will notice that a water will start to separate. I find that in my hand mixer with medium speed setting, it takes 3-4 minutes to get to the right texture. Mixer speed setting could vary, so, watch carefully to the texture of your whipped cream. Start paying attention on 2-3 minutes stage.
- Keep a close eye on the consistency – Never walk away from a machine while cream is whipping or you will end up with a homemade butter instead. You don’t want it to reach the point where it starts to get really thick and cloud like. When water starts to separate, there is no way to salvage for use as whipped cream. If that happens, just continue whipping and once the water separates, you will have a chuck of soft homemade butter. It is not your goal, but at least you don’t have to throw the entire batch.
- 5 large Egg – room temperature
- 3/4 cup (150 grams) granulated White Sugar, divided (1/2 cup for egg yolk mixture and 1/4 cup for egg white mixture)
- 1/2 teaspoon pure Vanilla Extract
- 1/2 cup (60 grams) plain Cake Flour
- 1/4 cup (35 grams) All-Purpose Flour
- 1 teaspoon Baking Powder
- 1/4 teaspoon Salt
- 3 tablespoons full fat Milk
- 2 tablespoons (28 grams) unsalted Butter
- Pastry Cream or Mousseline Cream
- 1/3 cup + 1 tablespoon Heavy Whipping Cream
- 1/3 cup + 1 tablespoon Chocolate (chopped or kisses)
- Preheat oven to 350 degrees F (177 degrees C) and place rack in center of oven. Butter and line the bottoms of two-8 inch (23 cm) round cake pans with parchment paper.
- Alternatively, you can bake it in a 9-inch round cake pan. You have to slice it into half later when adding the filling.
- Separate the Egg White and Egg Yolks: While the eggs are still cold separate three (3) of the eggs, placing the yolks in one bowl and the whites in another bowl. To the yolks, add the two (2) remaining eggs. Cover the bowls with plastic wrap and allow the eggs to come to room temperature (about 30 minutes).
- Dry Ingredients: Meanwhile, in a bowl whisk together the flours, baking powder, and salt.
- Melt the Butter: Place the milk and butter in a small saucepan, over low heat, and warm until the butter melts. Remove from heat, cover, and keep warm. You can also microwave the milk and butter for 15 seconds or until fully melted.
- Make the Cake Batter: In your electric mixer, fitted with the paddle attachment, (or with a hand mixer) beat the 2 whole eggs and 3 egg yolks and 1/2 cup (100 grams) of sugar on high-speed until they are pale and fluffy, about 9 minutes. When you slowly raise the beaters the batter will fall back into the bowl in a slow ribbon. Beat in the vanilla extract.
- Whisk the Egg White: In a clean bowl, with the whisk attachment, (or with a hand mixer) beat the egg whites at low-speed until foamy. Increase the speed to medium-high and gradually add the remaining sugar, beating until soft, moist peaks form.
- Cake Batter + Whisked Egg Whites: Gently fold a little of the whisked whites into the batter to lighten it, and then add the rest of the whites folding just until incorporated. Do this in 3 addition.
- Add Dry Ingredients: Sift half of the flour mixture over the top of the cake batter with egg whites and gently fold through with a rubber spatula or whisk. Sift the remaining flour over the batter and fold in.
- Add milk and Butter: Scoop about 1/4 cup of cake batter and mix it with the milk and melted butter mixture. This will help lighten the mixture for easy folding. Gently but thoroughly fold the butter mixture into the batter.
- Transfer in a Pan: Divide the batter evenly between the two pans and bake for about 21 minutes or until light brown and springy to the touch. A toothpick inserted in the middle will come out clean, and the side of the cake will slightly pull away from the side of the pan.
- Let Cool: Remove from oven and place on a wire rack to cool. Immediately run a spatula around the inside of the pans and then invert the cakes onto a wire rack. Remove parchment paper and re-invert. Cool completely.
- Make the Vanilla Custard Filling: Get the VIDEO recipe HERE. Transfer in a bowl and let the custard cool completely. Cover and refrigerate at least 1 hour.
- Make the Chocolate Ganache: Use the proportion specified in the ingredients section. Watch the VIDEO recipe HERE
- Fill and Frost the Cake: Level the top of the cake using a cake leveler or a sharp long knife. Set aside the scrap for snacking. Flip the cake, bottom facing up (the flat side). Spread custard filling on top. Cover with the other half of the cake, again, bottom side facing up. Run a spatula along the side in case there are some custard that spill. Spread the remaining custard filling on top. Chill for at least 30 minutes.
- Chocolate Ganache: For a cleaner frosting (optional), wrap the side of the cake with parchment paper to block the chocolate ganache from dripping on the side. Pour Chocolate Ganache and level. Return to the fridge and let chill for at least 30 minutes. This will allow the chocolate ganache to harden a bit. If you are not in a hurry to serve this, leave in the counter until the chocolate ganache is set. I usually leave this overnight. If you leave in a humid hot place, it is best to keep it refrigerated.
- Whipped Cream: This is optional, but I find that the addition of whipped cream on top elevated the taste of the cake, it brings all the flavor together. It is an extra step, but is totally worth it. You use store-bought whipped cream or make you own. Watch the VIDEO recipe HERE
Makes 8 servings
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