Put flour, 50 g sugar, salt, 120 g softened butter and egg into a mixing bowl. Warm the milk lukewarm, dissolve yeast in it and also put it into the mixing bowl. Knead with the dough hooks of the hand mixer for about 2 minutes to a smooth yeast dough. Cover and leave to rise in a warm place for 30-40 minutes.
Grease a springform pan (26 cm Ø). Put yeast dough on it and spread it evenly with your hands in the form. Cover and leave to rise in a warm place for another 20 minutes. Sort the blackberries, wash, dab dry and spread on the cake. Spread 50 g cold butter in flakes on the dough and sprinkle with 3 tbsp. sugar.
Bake the cake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 30 minutes. Cover with aluminium foil after about 20 minutes. Remove the cake and let it cool off or let it cool down. Whip cream until stiff and finally stir in advocaat. Serve cake with advocaat cream.
TIP: Enjoy the cake fresh the next day: Put the cake on a plate, cover with cling film and cook for about 30 seconds.