For the short pastry, knead 225 g flour, 75 g sugar, 1 pinch of salt, 1 egg and 125 g butter in pieces, first with the dough hooks of the mixer, then with lightly floured hands to a smooth dough. Wrap in foil and chill for about 30 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a springform pan (26 cm Ø). Separate 4 eggs. Beat the egg whites until stiff, then add 100 g sugar. Mix quark with egg yolk.
Mix pudding powder, 100 g sugar, 1 pinch of salt and vanilla sugar. Stir into the quark mixture. Fold in the beaten egg white.
Roll out the dough on a floured work surface until round (approx. 34 cm Ø). Line the mould with the dough, pressing lightly on the edges. Pour the curd mixture into the springform pan. Bake in the hot oven for approx. 1 1⁄4 hours on the lower rack.
Switch off the oven and let it rest for about 15 minutes with the oven door slightly open. Take out and carefully cut off the edge with a small knife. Let it cool down.