Make cake mix according to package directions. Bake in two 8 or 9 inch layer pan. Cool.
To make filling, drain the cherries, reserving the syrup. If needed, add water to the syrup to make one cup liquid.
Combine cornstarch and one cup liquid in saucepan. Cook until mixture thickens and clears.
Gently stir in cherries and sugar to taste if you like. Cool. Add brandy or brandy extract if using. Refrigerate.
To make topping, whip the whipping cream, gradually adding the powdered sugar, till stiff. Do not overbeat.
Cut cake layers in half, to have a total of 4 layers. To assemble, place one of the layers on cake platter. Form a rim of whipping cream around the outer edge. Fill the center with the cherry filling. Gently place remaining cake layers and repeat process. Cover top and sides of cake with remaining whipped cream.
Garnish with 1/3 bar sweet cooking chocolate, grated or shaved.