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 3/4 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 1/2 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.