This recipe is a simplified version of the traditional Boston Cream Pie that I make. They're equally delicious, but this version comes together quickly without the use of a mixer or the need to devote several hours of your day to the process. Instead, you can spend less time on the baking and more time enjoying the cake with someone you want to share it with.
Author: Jennifer from 1840 Farm
Ingredients
For the Vanilla Cake
4large eggs
1 ¼cupgranulated sugar
1teaspoonvanilla extract
2cupsAll-purpose flour
¼cupcornstarch
1Tablespoonbaking powder
½teaspoonsalt
1cupwhole milk or buttermilk(see substitutions below)
2ouncesoil (any neutral tasting oil will do. I like safflower.)
For the Pastry Cream
12ounceswhole milk
2largeeggs
pinchsalt
¼cupAll-purpose flour
6Tablespoonsgranulated sugar
1Tablespoonvanilla extract
For the Chocolate Fudge Topping
4ouncesheavy cream
2cupschocolate chips or chopped chocolate
Instructions
For the Vanilla Cake
Preheat the oven to 350° Fahrenheit. Position the oven racks in the top and bottom third of the oven. Prepare an oven safe 9x13 pan or casserole dish by coating with homemade magic pan release spreadand sprinkling with granulated sugar. Set aside as you prepare the cake batter.
I use whole milk, buttermilk, or whey leftover from making cheese or yogurt in this recipe. I use whatever I have on hand and need to find a use for. If you would like to use a buttermilk/whey substitute, you can measure out the cup of milk, remove one Tablespoon and replace it with a Tablespoon of white or apple cider vinegar. It will add the same tangy flavor to the cake as buttermilk or whey and the extra acidity will help the cake to rise.
In a large mixing bowl, combine the eggs, sugar, and vanilla extract. Stir with a wooden spoon or spatula until the mixture is well combined.
In a medium bowl, combine the flour, cornstarch, baking powder, and salt. I like to use a dry whisk to combine the dry ingredients and break apart any small lumps. You can sift them together if you prefer or skip the whisking/sifting entirely.
Add the buttermilk (or whatever substitute you are using) and the oil to the mixing bowl with the sugar and eggs. Stir to combine. Add the dry ingredients to the bowl in one addition and stir until the mixture is smooth and well combined with no visible streaks of flour in the batter.
Transfer the batter to the prepared baking pan. Transfer the pan to the preheated oven. Bake for 40-50 minutes, rotating halfway through the baking time. The cake is done when the top is lightly browned and a toothpick inserted into the middle of the cake comes out clean or with small crumbs attached.
Remove the cake from the oven to a wire rack to cool slightly. While the cake is cooling, make the pastry cream.
For the Pastry Cream
Place the whole milk in a medium saucepan. As the milk is warming, combine the eggs and dry ingredients in a medium bowl. Whisk to combine. The resulting batter should be thick and smooth.
Move the pan of milk from the burner. Slowly add the egg mixture while whisking to incorporate the thick batter into the warm milk.
Return the pan to medium low heat and bring to a simmer, whisking continuously until the mixture is thick enough to coat a spoon. Remove from the heat.
Transfer the pastry cream from the pan (straining if necessary to remove lumps) to a bowl. Add the vanilla extract and whisk to combine. Allow the mixture to cool slightly until it is warm to the touch but not steaming hot.
For the Chocolate Fudge Topping
Prepare the ganache by warming the heavy cream in a small pan or in the microwave in a microwave safe bowl for 30 seconds. Remove from the heat and add the chocolate. Allow the mixture to rest for two minutes before whisking to incorporate. When the cream and chocolate have become a thick, satiny mixture, it is ready.
To Assemble the Boston Cream Pie Sheet Cake
Using the end of a wooden spoon or a chopstick, poke several holes in the surface of the warm cake. This will allow the pastry cream to be absorbed by the cake and create a delicious, moist cake and pastry cream combination. Pour the entire batch of pastry cream over the cake, spreading it evenly to fully cover the surface of the cake.
Transfer all of the chocolate fudge topping to the pan. Spread the chocolate to fully cover the surface of the cake. If a bit of the pastry cream mixes with the chocolate, that's perfectly okay. It will still taste delicious.
Transfer the fully assembled cake to the refrigerator. The cake can be kept in the refrigerator for several days, although it never lasts that long at our house!
Notes
This cake benefits from the use of cake flour. Due to food allergies, I struggled to find a brand of cake flour that was safe to use in our kitchen. Fortunately, I discovered that I could combine All-purpose flour and cornstarch to deliver the benefits of cake flour without adding allergens to our kitchen and one more specialty ingredient to our pantry. For each cup of cake flour called for in a recipe, simply weigh out one cup of All-purpose flour, remove 2 Tablespoons of the flour and add 2 Tablespoons of cornstarch. You can learn more about this homemade substitute for cake flour and why it works here.