Banana Chocolate Cake

Preheat the oven to 180°C (top/bottom heat) or 160°C (fan). Line a springform pan (Ø 26 cm) with baking paper.
Beat the eggs, sugar, and salt for at least 4 minutes until frothy. Mix the flour and cocoa powder together, then fold into the egg mixture. Pour the batter into the pan and bake in the lower third of the oven for about 25 minutes. Let cool completely.
Place the chocolate sponge on a cake platter and surround it with a cake ring. Mix the crème fraîche with sugar and vanilla sugar until smooth. Soak the gelatin according to the package instructions, squeeze it out, and dissolve it with 2–3 tablespoons of the cream mixture.
Stir the warm gelatin mixture into the rest of the cream. Whip the heavy cream until stiff and fold it in. Peel and halve the bananas.
Place the banana halves cut side down on the sponge base, leaving a 1 cm border around the edge. Spread the cream over the bananas and smooth it out. Chill.
Chop the couverture chocolate. Bring the heavy cream to a boil, pour it over the chocolate, let it melt, and stir until smooth. Let the glaze cool for 2–3 minutes, then pour it over the cake and spread evenly. Refrigerate for at least 1 hour.