Sort blueberries. Separate 1 egg and keep the egg white for the meringue. Knead 200 g flour, 50 g sugar, 125 g butter, egg yolk and about 1 tablespoon cold water to a smooth shortcrust pastry.
Wrap in foil and chill for about 30 minutes. Meanwhile melt 50 g and let it cool down. Separate 7 eggs. Put 2 egg whites to the other stored egg white in a mixing bowl. Beat the remaining 5 egg whites until stiff and finally add 30 g sugar.
Mix the egg yolks, quark, 150 g sugar, vanillin sugar, coffee powder, 15 g flour and cornstarch. Gradually stir in liquid butter. Then carefully fold in the beaten egg white. Roll out the short pastry and line a greased springform pan (26 cm Ø) with it so that the edge of the pastry is 4-5 cm high.
Prick the bottom of the dough several times with a fork. Spread about 1/4 of the quark mixture on the base, sprinkle with the blueberries and add the rest of the quark mixture. Brush smooth. In the preheated oven, 2.
Bake from below (electric oven: 175 °C/ convection oven: not suitable/ gas: level 2) for approx. 1 hour. Beat the remaining 3 egg whites until stiff, while letting the 120 g sugar trickle in. After 45 minutes, spread the meringue loosely on the cake.
Finish baking the cake and leave it in the switched off oven for another 5 minutes. Let the cake cool completely in the tin. Then remove from the mould and decorate with blueberries and dust with coffee powder.