To make the butter-cream filling, beat together sugar and butter until well blended. Add egg yolk; beat until light and fluffy, about 3 to 5 minutes. Fold in Kirsch. CAKE ASSEMBLY: To assemble cake, place 1 layer on a cake plate. Spread with butter cream filling. Using 0.75 cup of the cherries, which have been patted dry, drop cherries evenly over cream. Place second layer on cake. Repeat. Place third layer on top. Fold 2 T confectioners' sugar into the whipped cream. Cover the sides and top of the cake with whipped cream. Decorate top of cake with remaining half cup cherries. To make chocolate curls from chocolate bar, shave (at room temperature) with a vegetable peeler. Refrigerate curls until ready to use. Press chocolate curls on sides of cake and sprinkle a few on the top. Chill until serving time.