Cook the Book: Boston Cream Pie

For the cake, preheat oven to 400°.

Put the eggs and sugar in the bowl of a standing mixer fitted with a whisk, and beat for 15 minutes. (Be patient; this long beating is what makes this cake so light and delicate.)

Sift together the cake flour, pastry flour, salt, and nutmeg. Gradually add the dry ingredients to the beaten eggs while continuing to whisk.

Add the milk and vanilla.

Grease two 8½-inch round cake pans and dust them with flour, tapping out any excess. Divide the batter between the 2 pans and bake until the tops are golden and a skewer poked into the center of the cakes comes out clean, 17–20 minutes. Unmold the cakes onto wax paper or parchment paper that has been sprinkled with sugar.

For the custard, heat 1½ cups of the milk and the sugar in a heavy saucepan over low heat, stirring until the sugar dissolves.

Whisk together the remaining 1 cup milk, cornstarch, egg yolks, salt, vanilla, and Grand Marnier, if using. Gradually add it to the hot milk, stirring with a wooden spoon until the custard is thick and smooth, about 20 minutes. Keep heat low and stir from the bottom of the pan so the custard doesn’t scorch. Stir in the butter then set aside to cool.

For the chocolate icing, heat the chocolate and cream in a small heavy pan over low heat, stirring until melted and smooth (or heat for about 1 minute in the microwave, then stir the cream and chocolate together).

To assemble, split each cake into 2 layers, spread the bottom layers with cooled custard, put on the top layers, and spread chocolate icing evenly over the tops.