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 juice. If needed, add water to the juice to make one cup liquid.
Combine cornstarch and one cup juice 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.
To assemble, place one layer on cake palter. Form a rim of whipping cream around the outer edge. Fill the center with the cherry filling. Gently place top layer on top of filling. Cover top and sides of cake with remaining whipped cream.
Garnish with 1/3 bar sweet cooking chocolate, grated or shaved.