Boston Cream Parfaits

Custard 1/2 cup sugar 2 cups milk 1 tspn vanilla 4 egg yolks 6 tspn cornstarch OR 1 box vanilla pudding (4 servings size)

Chocolate Layer 2/3 cup sugar 1/3 cup cocoa 3 tbsp cornstarch pinch of salt 2 1/4 cups milk 1 tbsp butter OR 1 box (4 servings size) chocolate pudding mix

Yellow Cake 3/4 cup butter 3 eggs 2 1/2 cups flour 2 1/2 tbsp baking powder 1/2 tbsp salt 1 1/2 cups sugar 2 tbsp vanilla extract 1 1/4 cups milk OR 1 box yellow cake mix prepared in 9x13 pan Topping 2 cups heavy cream 1 tbsp vanilla 1/4 cup sugar chocolate sauce