package (18-1/4 ounces) yellow cake plus ingredients to prepare
1. Preheat oven to 350°F. Grease two 9-inch round cake pans.
2. Following package directions, prepare and bake cake in prepared pans. Cool cakes in pans 10 minutes. Loosen edges of cakes and remove to rack to cool completely.
Meanwhile, prepare Cream Filling. When filling is cool, prepare Chocolate Glaze. To assemble, place one cake layer on plate. Spoon Cream Filling over cake layer; cover with second layer. Spread top with Chocolate Glaze; cool. Serve when glaze is completely set. Refrigerate leftovers.
Combine 1/3 cup granulated sugar, 2 tablespoons cornstarch and 1/4 teaspoon salt in 2-quart saucepan. Gradually stir in 1-1/2 cups milk. Cook over medium heat, stirring constantly, until mixture thickens and comes to a boil. Boil 1 minute, stirring constantly. Gradually stir small amount of hot mixture into 2 slightly beaten egg yolks; mix thoroughly. Return to hot mixture in pan. Bring to a boil; boil 1 minute, stirring constantly. Do not overcook. Remove from heat; stir in 2 teaspoons vanilla. Cool to room temperature.
Combine 2 (1-ounce) squares unsweetened chocolate and 3 tablespoons butter in medium saucepan; stir over low heat until melted. Remove from heat; stir in 1 cup sifted powdered sugar and 1 teaspoon vanilla. Stir in 3 to 5 teaspoons water, 1 teaspoon at a time, until glaze is of desired consistency. Cool slightly.