Separate eggs. Cream egg yolk, 2 tablespoons of hot water and 50 g sugar. Beat the egg whites until stiff, slide them onto the egg cream. Sift the flour and baking powder over it and fold in carefully
Pour the mixture into a springform pan (22 cm Ø) lined with baking paper and smooth it down. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 10-12 minutes. Remove the base from the pan, turn onto the cake rack and remove the baking parchment immediately. Let the base cool down. Soak the gelatine in plenty of cold water. Stone and chop plums, except for one fruit
Season soured milk with the rest of the sugar. Squeeze the gelatine, dissolve and stir into the soured milk. Put it in a cold place. Whip 200 g cream until stiff. As soon as the soured milk begins to gel, fold in the cream and plum pieces
Cut the bottom once. Place the edge of the springform pan around the lower sponge cake. Spread plum cream on top. Cover with second base. Chill for about 2 hours. Stone the rest of the plum and cut into slices. Whip 100 g cream until stiff and fill into a piping bag with star-shaped spout. Decorate cake with plums, cream tuffs and mint