Take 6 glasses. Cut 12 circles from the cake with the help of a glass. Beat the egg whites until fluffy. Mix 1 cup of coffee with 50 gram kahlua. Melt the chocolate in the microwave with the rest of the coffee. Beat in the sugar and the kahlua. Stir in the egg yolks and the rest of the kahlua. Add the egg whites carefully. Put two tablespoons of the mixture in each glass. Put a slice of cake on top and drizzle with the coffee-kahlua mixture. Add another few tablespoons of the mascarpone mixture, put the second slice of cake on top and drizzle with the coffee mixture. Add the rest of the mascarpone mixture. Decorate with a piece of chocolate.