Decadent and rich.
Preheat oven to 300°F. Spray three 9-inch round cake pans with cooking spray. Lightly dust with additional corn starch.
Combine chocolate and butter in large saucepan over low heat, stirring frequently, just until chocolate melts. Pour into large mixing bowl; cool to room temperature.
Beat egg whites in large mixer at high speed. Gradually add sugar, beating until soft peaks form. Stir egg yolks into chocolate mixture; add corn starch and vanilla. Fold egg whites into chocolate mixture until thoroughly blended. Pour into prepared pans.
Bake for 35 to 40 minutes or until cakes are set. Remove from oven and run a knife around the edge of each pan. Cool on a wire rack.
Sprinkle with powdered sugar before serving. Drizzle with chocolate, caramel or a favorite fruit sauce. Or serve with a dollop of whipped cream and fresh berries.