Coarsely chop the chocolate coating and melt it over a warm water bath. Leave to cool for about 5 minutes. Grease the bottom of a springform pan (26 cm Ø) and dust with flour
Separate eggs. Beat the egg whites and 3 tablespoons of cold water with the whisk of the hand mixer until stiff, then gradually add sugar, vanillin, sugar and salt. Add egg yolks one after the other and fold in. Add the liquid chocolate coating while stirring. Mix flour, starch and cocoa, sieve onto the egg foam and fold in carefully with a dough scraper.
Put the sponge mixture into the springform pan and smooth it down. Bake in the preheated oven, 2nd shelf from below (electric oven: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-18 minutes. Let the sponge cake cool down in the tin on a cake rack for about 3 hours. Remove the sponge cake from the tin and cut through horizontally once
Peel and slice the bananas and sprinkle with lemon juice. Beat 200 g cream with 1 1/2 tbsp. icing sugar until stiff. Spread 1/2 of the whipped cream on the bottom layer. Dab the bananas, spread on the cream and spread the rest of the whipped cream on top. Carefully place the second base on top
Whip 400 g cream with 3 tbsp. icing sugar until stiff, fold in grated chocolate. Using a tablespoon, spread loosely and on the cake. Refrigerate for another 30 minutes. Decorate cake with mint
waiting time approx. 3 1/2 hours