Warm the milk lukewarm. Dissolve yeast in it. Knead flour, 75 g soft fat, egg, 60 g sugar, vanillin sugar, salt and yeast milk. Cover and leave to rise in a warm place for 30-40 minutes.
Melt 150 g of grease for the topping. Dissolve 100 g sugar in it, do not brown. Pour on 250 g cream. Stir in hazelnut flakes and oat flakes. Leave to cool. Roll out the dough on a greased baking tray, spread nut mixture on top.
Bake in the preheated oven (electric oven: 175 °C/ gas: level 2) for 30-35 minutes. Let them cool down. Clean, wash and chop the rhubarb. Wash the lemon and peel the rind in a spiral.
Boil up rhubarb, grape juice, 1/8 litre water, cinnamon and lemon peel. Mix cornflour with a little water and thicken the compote. Bring to the boil and season to taste with 100 g sugar. Remove cinnamon stick and lemon peel.
Let it cool down a little. Cut bee sting crosswise into 4 approx. 9 cm wide strips and halve horizontally. Fold the aluminium foil into a bar of approx. 5 cm height and place around the 4 lower strips. Spread the rhubarb on the lower strips and let it cool down.
Whip the remaining cream with the remaining sugar and vanilla pulp until stiff. Soak, squeeze and dissolve the gelatine. Stir into the cream. Spread on the Rha-barb layer, chill. Cut the upper bee sting strips into 6 pieces.
Loosen aluminium foil. Cut the lower strips into 6 pieces as well. Place the upper pieces on top. Results in about 24 pieces.