Source  Betty Crocker

Recipe Added:  1/11/2015

Cream Filling
Separate two egg yolks then beat in a bowl with a wire whisk until blended. Stir in 1 1/2 cups milk; set aside. In a 2-quart saucepan, stir together 1/3 cup sugar, cornstarch and 1/8 tsp salt. Gradually stir egg mixture into sugar mixture. Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir 1 minute; remove from heat. Stir in 2 tsp vanilla. Press plastic wrap on surface of filling to prevent a tough layer from forming on top. Refrigerate at least 2 hours until set but no longer than 24 hours. While filling is chilling, continue with cake.

Cake
Heat oven to 350°F. Spray bottom of 9" round cake pan with the baking spray. In a large bowl, beat all cake ingredients with an electric mixer on low speed 30 seconds, stopping frequently to scrape batter from sides of bowl. Beat on high speed 3 minutes, stopping occasionally to scrape bowl. Pour batter into pan and smooth top. Bake 30-35 minutes or until toothpick inserted comes out clean. Cool cake in pan on a cooling rack 20 minutes, then remove onto cooling rack to finish cooling completely, about 1 hour.

Chocolate Icing
In a saucepan, melt butter and chocolate over low heat, stirring occasionally. Meanwhile, in 1-cup glass measuring cup, microwave 4 Tbsp water uncovered on High 15 to 30 seconds or until hot. Remove chocolate from heat. Stir in powdered sugar and vanilla. Stir in 3 Tbsp hot water. Stir in additional water, 1 tsp at a time, until icing is smooth and thin enough to spread.

Finish
To split cake horizontally in half, mark middle points around side of cake with toothpicks. Using toothpicks as a guide, cut through the cake with a long, sharp knife, using a back-and-forth motion. On a serving plate, place bottom layer with the cut side up. Spread filling over bottom layer. Top with top of cake, cut side down. Spread glaze over top of cake, letting some glaze drizzle down sides. Refrigerate uncovered until serving. Store any remaining cake covered in the refrigerator.

The earliest reference to a cream filled cake is Chocolate Petit Pains found in an 1832 Boston cookbook. This is a recipe for chocolate covered petite fours. In an 1845 New York cookbook is a recipe called Trifle Cake. A Rice Cake made with rice flour has its top cut off and filled a layer of custard, jam, and frothed (whipped) egg whites. In an 1855 Boston cookbook a recipe called Boston Cream Cake appeared. The recipe has no sugar, it is a muffin or biscuit which was split and buttered. One or all three may have contributed to what eventually became known as Boston Cream Pie.

1. http://www.bettycrocker.com/recipes/boston-cream-pie/866fb98f-be51-4e87-a746-86f042691094

2. http://www.newenglandrecipes.org/html/boston-cream-pie.html