Boston Cream Pie
Boston Cream Pie is certainly not a pie but instead is a tender two-layered cake, with a luscious pastry cream filling topped with a dreamy chocolate glaze. So why is it called a pie?
In the nineteenth century, when Boston Cream Pie was born, many cakes were baked in shallow, straight-sided pans called Washington pie plates or jelly-cake tins. Pie tins and cake tins were the same thing. So the word “pie” stuck.
The earliest Boston Cream Pies are from the late eighteen hundreds. They were two-layered cakes filled with pastry cream or custard and simply dusted on top with powdered sugar. Their signature chocolate icings weren’t created until much later, in the 1930s. Possibly earlier. The lag time between practice and print can be considerable.
My recipe spans the nineteenth and twentieth centuries. The cake, a hot milk sponge, is an oldie that combines the tenderness of a butter cake with the airiness of a sponge cake. It’s easy to make and tastes great. And instead of baking two layers, you bake one and split it.
The pastry cream is a classic nineteenth century recipe made more modern and extra smooth with egg yolks and a little heavy cream. And the chocolate glaze is a popular twentieth century ganache—chocolate melted in heavy cream—which takes hardly any work at all.
Boston Cream Pie is wonderful any time of the year and for any occasion. How about right now? It’s no surprise that in 1996 it was proclaimed the Official State Dessert of Massachusetts.
Boston Cream Pie
- 1 cup whole milk
- 2 tablespoons cornstarch
- 1/4 cup heavy cream
- 3 large egg yolks
- 1/8 teaspoon salt
- 1/3 cup sugar
- 2 tablespoons cold butter, cut into 4 pieces
- 1 1/2 teaspoons vanilla
Hot Milk Sponge Cake
- 1 cup sifted cake flour (3 1/2 ounces)
- 1 teaspoon baking powder
- 1/4 teaspoon salt
- 1/2 cup whole milk
- 4 tablespoons butter (1/2 stick)
- 2 large eggs
- 2 large egg yolks
- 2/3 cup sugar
- 1 1/2 teaspoons vanilla
- 1/4 cup heavy cream
- 1 tablespoon light corn syrup
- 3 ounces semisweet or bittersweet chocolate, chopped
Make Pastry Cream
- To make the pastry cream, stir 1/4 cup of the milk with the cornstarch in a small cup or bowl and set it aside. Bring the remaining 3/4 cup milk and 1/4 cup cream to the boil in a small saucepan over medium heat—watch it closely so it doesn’t overflow—and set it aside.
- In a medium bowl, whisk the egg yolks with the salt just to mix. Gradually add the sugar while whisking vigorously for a minute or two until the yolks are very thick and pale in color. Very slowly—a tablespoon or so at first—add the hot milk and cream to the yolks, whisking constantly. Give the cornstarch/milk combo a stir and whisk it in. Transfer to a medium saucepan.
- Cook over medium heat, stirring and scraping the sides and bottom of the pan constantly with a heatproof flexible spatula. As the custard heats up, add the butter pieces one at a time, and continue cooking—stirring all the while, especially the bottom of the pan—until the custard thickens and holds its shape. This step takes about 5 to 8 minutes. The pastry cream won’t actually boil, but you might see a bubble or two break the surface. Lower the heat and cook, stirring gently a minute or two more. Take the pan off heat, stir in the vanilla, and scrape the pastry cream into a bowl. Press a piece of plastic wrap right on the cream and refrigerate until cold, about 2 hours. You can make the pastry cream the day before and keep it refrigerated.
Make the Cake
- Adjust an oven rack to the lower third position and preheat the oven to 350 degrees. Butter or coat with cooking spray a 9-inch layer cake pan. Line the bottom with a round of cooking parchment or waxed paper. Butter the paper or coat with cooking spray and dust the inside of the pan lightly with all-purpose flour. Knock out excess flour.
- In a medium bowl, whisk the cake flour with the baking powder and salt and set aside.
- Place the milk and butter in a small heavy saucepan and set overlow to medium heat. The milk and butter must get very hot while the eggs beat, and it's important the liquid is ready at about the same time as the eggs or the eggs may deflate.
- Beat the eggs and yolks with an electric mixer on high speed for about 5 minutes until thickened and light in color. Reduce the speed to medium and add the sugar 1 tablespoon at a time, beating for 10 to 15 seconds after each addition. Once all the sugar has been added, increase the speed to high and beat for 5 minutes. Beat in the vanilla. On low speed, add the dry ingredients and beat only until incorporated. Scrape the bowl, handling the batter as gently as possible.
- Quickly bring the milk and butter mixture to the boil. While beating on low speed, add the liquid in a steady stream to the batter, taking 15 to 20 seconds to do so. Don't dally. As soon as the batter is smooth scrape it into the prepared pan and place the pan in the oven.
- Bake 25 to 30 minutes, until the top of the cake is a deep golden brown color, it springs back when gently pressed, and the cake just begins to pull away from the sides of the pan. Do not over-bake. Cool for 10 minutes on a wire rack. If the cake is sticking at any point to the side of the pan, release it with the tip of a small sharp knife. Cover the cake with a wire rack and invert. Remove the pan and paper liner. Cover the cake with another rack, and re-invert so that the cake cools right side up. The layer will be about 1 inch high.
Assemble the Dessert
- To assemble the dessert, use a sharp serrated knife to divide the cake in half horizontally. Carefully remove the top half and set it aside. Place the bottom half, cut side up, on a dessert platter or cake plate. Stir the cold pastry cream gently to smooth it out. Spoon it onto the cake and spread it slowly with a small metal spatula to make a smooth layer reaching the edge of the cake. Set the top half of the cake cut side down onto the filling. If you want to serve the cake soon with an unchilled filling, leave it at room temperature while you make the ganache, otherwise refrigerate it.
Make the Ganache
- Bring the 1/4 cup cream and corn syrup to the simmer in a small heavy saucepan over medium heat. Add the chocolate, stir briefly with a small whisk until the chocolate is partly melted, and remove the pan from the heat. Continue stirring until the glaze is melted and very smooth. Set the glaze aside for a few minutes, stirring occasionally, until it has thickened a bit. To glaze the cake, pour all of the ganache onto the center of the cake and carefully spread it with a long metal spatula right to the edge of the cake allowing some of the glaze to dribble down the sides. Refrigerate for a few minutes to set the glaze or for 1 to 2 hours (or longer, even overnight). Cut into portions with a knife rinsed in hot water and serve.