Boston Cream Poke Cake

5 from 1 vote

This dreamy Boston cream poke cake transforms the classic Boston cream pie into a super moist vanilla cake oozing with creamy pastry cream and topped with a decadent chocolate ganache!

Prep Time1

Cook Time35

Chilling time4

Total Time2 35

Course: Dessert

Cuisine: American

Servings:

Calories: 850kcal

Author: Katalin Nagy

Equipment

Ingredients

Vanilla Sheet Cake

300 g Granulated sugar
113 g Unsalted butter at room temperature
110 g Oil
3 Eggs at room temperature
240 g Greek Yogurt at room temperature
1 teaspoons Vanilla extract
375 g All purpose flour
½ teaspoon Salt
1 teaspoon Baking powder
1 teaspoon Baking soda

Pastry Cream

960 g Whole milk 3% fat
200 g Granulated sugar
160 g Egg yolk approximate yolk of 8 eggs
50 g Corn starch
50 g All purpose flour
½ tablespoon Vanilla extract
110 g Unsalted butter 82% fat, at room temperature
115 g Heavy cream 36% fat content, cold - this will be used to make the diplomat cream frosting

Chocolate ganache

230 g Semi-sweet chocolate
230 g Heavy cream 36% fat content
1 tablespoon Vegetable oil

Metric - US Customary

Instructions

Vanilla Sheet Cake

Preheat your oven to 175℃ / 350℉ (no fan) and grease a 9x13-inch / 22x33 cm pan or line it with parchment paper on the bottom and sides for easy removal.
In a large bowl, cream the room-temperature butter and sugar for a few minutes until light and fluffy. Next, add the oil, and then the room-temperature eggs one at a time, mixing well after each addition. Then, mix in the room-temperature yogurt and vanilla extract.
Sift the dry ingredients—flour, baking powder, baking soda, and salt—into the butter mixture. Gently fold them in with a rubber spatula until just combined. Be careful not to overmix the batter.
Pour the batter into the prepared baking pan and smooth the top with an offset spatula. Bake for about 35 minutes at 175℃ / 350℉, or until a toothpick inserted into the center comes out clean. Be sure not to overbake it, as this can cause the cake to dry out.

Pastry cream

About halfway through the baking time, begin making the pastry cream. Whisk the sugar and egg yolks together in a bowl for 1-2 minutes until the mixture is light and fluffy. Then, add the cornstarch, flour, and vanilla, and mix until smooth.
In a saucepan, heat the milk over medium heat until it starts to simmer (but not boil). Slowly pour the hot milk into the egg yolk mixture, whisking constantly to temper the yolks.
Return the mixture to the saucepan and cook over medium heat, stirring continuously, until it thickens—this should take about a minute after boiling. If the mixture is lumpy, keep whisking until smooth. Remove from heat and strain if necessary.
Gradually add the softened butter, mixing until fully incorporated.
Divide the pastry cream in half. One portion will be used to fill the holes of the poke cake while the cream is still hot, and the other half will be reserved for frosting. For the frosting part, cover it with plastic wrap and let it come to room temperature.

Poke the cake

As soon as the sheet cake is done baking, take it out of the oven and use the handle of a wooden spoon to poke holes all over the top. Pour half of the pastry cream all over the cake, making sure to fill in the holes.
Let the cake come to room temperature before frosting.

Diplomat cream frosting layer

Once the other half of the pastry cream is cooled to room temperature, begin preparing the frosting, which will be a diplomat cream; pastry cream lightened up with whipped cream.
Place very cold 36% fat-content heavy cream in a mixing bowl and use an electric hand mixer to whip the mixture for about 2-3 minutes until fluffy. Do not overwhip.
Gently loosen the pastry cream with a few quick whisks, then carefully, using a rubber spatula, fold in the whipped heavy cream, ensuring the mixture stays light and airy. Immediately spread the frosting on top of the cake and smooth the top with an offset spatula. Refrigerate while preparing the chocolate ganache glaze.

Chocolate ganache glaze

Semi-melt the chocolate in the microwave. Meanwhile, heat the cream in a saucepan until it just begins to simmer. Pour the simmering cream over the melted chocolate and stir until smooth, then stir in the oil. Set aside and allow the glaze to cool to about 30°C (86°F). It should have a smooth consistency—neither too runny nor too thick—before spreading it all over the cake.
Pour the chocolate ganache glaze over the cake and smooth with a spatula. Chill the cake for 4 hours before serving.
Serve the Boston cream poke cake after the 4 hours of chilling time. Any leftovers can be covered and stored in the refrigerator for 1-2 days.

Notes

Ingredient notes:

Measure your ingredients with a digital scale for accuracy.
All cake ingredients must be at room temperature to properly emulsify: eggs, butter, and yogurt.
Good quality butter and pure vanilla extract are the heart of making pastry cream. Use high-quality 82% fat-content European butter and the best quality vanilla you can access.
For the whipped cream, high-fat (36%) heavy cream is recommended, and it should be used very cold. Cream with a lower fat content might not whip up properly.

Technique notes:

Baking this cake takes 35 minutes in my oven. However, you should focus on the texture, not the time. Apply the toothpick test (it should come out clean) to avoid overbaking your cake - that would result in a dry texture.
Use a small/medium-sized saucepan with good heat distribution to avoid burning the milk when making pastry cream.
Whipped cream frosting is very easy to overwhip. When whipping, stop as soon as the mixture has reached a fluffy consistency and stiff peaks. It won't get stiffer after this point. In fact, if you overbeat it, it will only get runnier, and then it will break.
Pay attention to the equipment mentioned in the recipe, when to use a mixer, and when to use the rubber spatula.

Nutrition