Line the bottom of a springform pan (20 cm Ø) with baking paper. Put the lady fingers in a freezer bag, close it and roll it over with a cake roll until the sponge fingers are finely crumbled.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Chop 100 g chocolate and melt in a hot water bath.
Separate eggs. Beat the egg whites and 1 pinch of salt with the whisks of the mixer until stiff, adding 50 g of sugar. Stir 100 g butter and 50 g sugar for about 5 minutes until creamy. Stir in the egg yolks one by one.
Add liquid chocolate while stirring. Mix flour, cocoa and sponge fingers and stir in. Fold in portions of beaten egg white. Smooth the dough into the mould. Bake in a hot oven for about 30 minutes.
Take out, let it cool down.
Warm the jam and pass through a sieve. Remove the cake base from the tin and cut in half horizontally with a long knife. Spread half of the jam on the lower cake base, place the second cake base on top.
Spread the cake all around with the remaining jam and let it dry for about 2 hours.
Chop 100 g chocolate. Bring the cream to the boil and remove the pot from the stove. Melt 20 g butter and chocolate in it. Bring 30 ml water and 50 g sugar to the boil in a small pot and simmer until the sugar has dissolved.
Take the pot off the stove. Add the chocolate cream while stirring. Spread the icing evenly on the cake and the edge. Chill for about 30 minutes.