1. Start with the chocolate sponge cake. Beat egg whites, cream of tartar and salt in a bowl until foamy.
2. Add the sugar slowly and continue beating until stiff peaks.
3. Fold in egg yolks and vanilla and continue beating until thoroughly mixed.
4. Combine flour and cocoa and add them slowly through a sieve in the mixture while mixing.
5. Line a 20-inch square baking pan with parchment paper and pour the batter in on a thin layer.
6. Bake in a preheated oven at 325 F for 20 minutes.
7. Let the sponge cake cool down and refrigerate.
8. Cut the cold cake with a 3-inch pastry ring.
You should get at least 20 rounds.
9. Wrap the walls of ten 3-inch pastry rings with plastic wrap and arrange them on a tray lined with parchment paper.
10. Place one slice of sponge cake on the bottom of each ring.
11. Top with (click to see the recipe) chocolate mousse and repeat one more time.
12. Refrigerate for 2 hours.
13. In the meantime, melt the semi-sweet chocolate with the cream and vanilla over double boiler, then cool it down to 45 C.
14. Pour the chocolate topping over each mousse cake, sprinkle with white chocolate shavings and refrigerate for 1 hour more.
15. Before serving pull up gently the pastry rings from around the chocolate mousse cakes.