How to Make It
Coat a 9-inch round cake pan with cooking spray, and line bottom with wax paper. Set aside.
Cream margarine, and gradually add 1/2 cup sugar, beating well at medium speed of a mixer. Add vanilla and egg yolk; beat well. Combine flour, baking powder, and salt; add to creamed mixture alternately with milk, beginning and ending with flour mixture. Mix after each addition.
Beat the egg whites (at room temperature) at high speed of a mixer until foamy. Gradually add 3 tablespoons sugar, 1 tablespoon at a time, beating until stiff peaks form. Gently stir one-fourth of egg white mixture into batter. Gently fold in remaining egg white mixture. Pour into prepared pan. Bake at 350° for 35 minutes or until cake springs back when touched in center. Let cool in pan 5 minutes on a wire rack, and remove from pan. Peel off wax paper; let cool completely on wire rack.
Using a serrated knife, split cake in half horizontally. Place bottom layer, cut side up, on a serving plate. Spread Vanilla Pastry Cream over bottom cake layer; top with remaining cake layer. Spread Chocolate Glaze over top of cake. Chill 1 hour or until glaze is set.