Opera-style Cake Squares

For Sponge Cake:

Preheat oven to 350º F / 180º C. Line a 10 1/2 x 15 1/2-inch / 27 x 39 cm sheet pan with parchment paper.

Separate the eggs, into 2 separate bowls. Using an electric mixer, beat egg yolks with 1/2 cup sugar until foamy; beat in the vanilla. Beat the egg whites until soft peaks form. Slowly add the remaining sugar, beat until stiff peaks form. Place the egg whites on top of egg yolk mixture.

Sift flour and cornstarch over egg mixture and carefully fold mixtures together. Turn batter out into prepared pan, and bake 30 to 40 minutes or until a toothpick inserted in center comes out clean. Remove from oven, allow to cool slightly. Run knife around inside edge of pan to carefully loosen cake. Transfer cake to a cooling rack to cool completely, about 2 hours. Once cool, slice the cake horizontally creating 3 equal layers.

For Vanilla Buttercream Frosting:

Combine butter, sugar and salt. Beat until blended. Add the milk and vanilla and beat for an additional 3 to 5 minutes, or until smooth and creamy.

Spread frosting over cooled layers; stacking into three layers.

For Chocolate Ganache:

In a small saucepan, over medium-high heat, bring the cream to a boil. In a ovenproof bowl, combine the chopped chocolate, corn syrup and butter. Pour the hot cream over the chocolate mixture and let stand for 5 minutes, or until the chocolate melts. Whisk until smooth and creamy. Let the glaze cool for about 5 minutes, or until thick, but still spreadable.