Boston Cream Pie

Martha Stewart Living

Makes one 9-inch cake

    SPONGE CAKE:                                                   
    Unsalted butter for cake pan                                   
    1 cup sift cake flour (not self rise)                          
    1/4 teaspoon salt                                              
    4 eggs                                                         
    1 cup sugar                                                    
    1/4 cup + 2tbsp milk                                           
    1 vanilla bean split LW  
                                      
    CREAM:                                                         
    6 lg. egg yolk                                                 
    3/4 cup sugar                                                  
    6 1/2 tablespoons cornstarch                                   
    1/8 teaspoon salt                                              
    3 cups milk                                                    
    2 teaspoons vanilla extract 
                                   
    GLAZE:                                                         
    4 ounces semisweet chocolate bar coarse chop                   
    1/2 cup heavy cream                                            

This American classic, first made by a Boston chef in the 1850s, isn't actually a pie at all, it's a cake: two sponge layers with custard-cream filling and a shiny chocolate glaze. This recipe calls for a 9-by-2-inch cake pan; if you use an 8-inch wide pan, the batter will overflow.

CAKE:
Heat oven to 350°. Lightly butter and flour a 9-by-2-inch round cake pan. Line with parchment paper; set aside.

Sift together cake flour and salt. Sift again, twice; set aside. In the bowl of an electric mixer fitted with the whisk attachment, mix eggs and sugar until well combined. Place the bowl over a pot of gently simmering water; whisk until mixture is warm, about 110°, and sugar is dissolved, about 6 minutes. Remove from heat; place bowl on mixer. With the whisk attachment, beat egg mixture on high until thickened and pale, about 6 minutes.

Meanwhile, in a small saucepan, combine milk and split vanilla bean. Place over medium heat until hot, being careful not to let boil. Remove and discard vanilla bean. With egg mixture beating, pour hot milk into egg mixture in a slow, steady stream. Turn off mixer. Transfer to a medium bowl; fold in flour mixture. Pour into prepared pan.

Bake until cake is golden brown and springs back when gently pressed, about 30 minutes. Transfer to a wire rack to cool for 15 minutes. Remove from pan; cool completely.

FILLING:
Prepare an ice-water bath. In a large bowl, whisk egg yolks; set aside. In a medium saucepan, combine sugar, cornstarch, and salt. Gradually stir in milk. Cook over medium heat, stirring constantly, until mixture thickens and begins to bubble, about 5 minutes. (It is essential that mixture come to a boil.) Remove from heat.

Whisking constantly, slowly pour hot milk mixture into egg yolks. Return mixture to saucepan. Cook over medium heat, stirring constantly, until mixture begins to bubble, about 3 minutes. (It is essential that mixture bubble again.) Remove from heat; stir in vanilla extract.

Transfer filling to a medium bowl. Place the bowl in the ice bath. Stir from time to time until mixture cools; it thickens as it cools. Cover with plastic wrap, pressing wrap against the filling to prevent a skin from forming. The filling may be refrigerated overnight at this stage, or it is ready to use.

GLAZE:
Split cake into two layers; spread bottom half with chilled filling. Place in refrigerator to set, about 30 minutes. Wrap remaining half of cake with plastic wrap; set aside.

In a medium-size heat-proof bowl, or the top of a double boiler, set over a pot of gently simmering water, combine chocolate and heavy cream. Stir occasionally until chocolate melts, about 12 minutes. Remove from heat; set aside to cool for 10 minutes.

Remove cake from refrigerator; top with reserved layer. Transfer cake to serving plate; pour chocolate glaze over top. Allow to set 20 minutes before serving.