Kalter Hund

Spread butter cookies out in a single layer on a baking sheet with sides. Brush or sprinkle with rum. Line a 9x5 inch loaf pan with aluminum foil, leaving enough extra at the sides to fold over the top for storage.

In a medium bowl, whip the egg and sugar together until thick and pale. Whisk in vanilla and cocoa powder until well blended, then stir in melted butter.

Line the bottom and sides of the prepared pan with butter cookies. Spread a 1/2 inch layer of chocolate cream over the bottom. Place another layer of cookies, followed by another layer of cream. Repeat until cream is gone, ending with cookies on the top. Fold aluminum foil over the top, and place in the refrigerator until firm, about 3 hours. Slice into 1/2 inch slices and serve.