Filling: Drain cherries, reserving 3/4 cup syrup.
Halve cherries and pour kirsch over; let stand at least 2 hours.
Place cornstarch in saucepan; gradually blend in reserved syrup; add cherry mixture.
Heat quickly till mixture thickens and comes to boiling, stirring constantly, then cook and stir 1 minute.
Cool.
Chill.
Butter cream: Beat butter and sugar together till smooth; beat in egg yolks and continue beating till light and fluffy.
Place one layer of spongecake on serving plate.
From 1 cup Butter cream, make a 1/2 inch border (1 1/4 inches high) around top of cake.
Use 1/2 cup Butter cream to make circle in center of cake, about 2 1/2 inches in diameter and 1 1/4 inches high (same height as border).
Spread chilled cherry filling between border and center of Butter cream.
Place second cake layer on top; press down just sufficiently to make layers stick together.
Cover top and sides of both layers with remaining Butter cream.
Sprinkle sides with chocolate shot, and the top with shaved chocolate; garnish with maraschino cherries.
Chill.
Let stand at room temperature about 20 minutes before serving.
Slice like a cake into 6 to 8 servings