Beat the eggs, 50 g sugar and vanilla sugar with the whisk of the hand mixer on a hot water bath until the sugar has dissolved. Then remove from the water bath and continue beating until the mixture has a firm consistency.
Sieve the flour and baking powder onto the egg cream and fold in. Line the bottom of a springform pan (26 cm Ø) with baking paper. Fill in sponge cake mixture and smooth it down. Bake in a preheated oven (electric: 200 °C/ gas: level 3) for about 20 minutes.
Take out, let it cool down a little, turn out of the tin, remove baking paper and let it cool down. In the meantime, clean and peel the rhubarb and cut it into pieces of about 3 cm. Simmer white wine, 50 ml water, raspberries, rhubarb skin and 100 g sugar for about 5 minutes.
Then pour through a sieve into a pot and bring to the boil. Stir the pudding powder into 1 tablespoon of water until smooth and thicken the rhubarb stock with it. Add the rhubarb and bring to the boil again. Let the compote cool down for about 30 minutes.
Whip the cream until stiff. Stir mascarpone, quark, liqueur and remaining sugar until smooth. Fold in the cream and keep cool. Halve the sponge cake base crosswise and cut one half into quarters. Use the rest of the sponge cake for other purposes.
Line a glass bowl (approx. 2 litres capacity) with the biscuit quarters (tips pointing upwards). Fill up with about half of the mascarpone cream. Spread rhubarb compote on top. Add the remaining mascarpone cream, smooth it down and put it in a cool place for about 1 hour.
Wash and clean the strawberries, drain, cut in half and spread on the cream.