Put the flour in a bowl and add the butter in pieces. Knead with the dough hooks of the hand mixer for 4-5 minutes until crumbly. Add sugar, vanillin sugar, egg yolk and sour cream and knead to a smooth short pastry. Then continue kneading SHORTLY with floured hands and form into an oblong loaf. Cut the dough into thirds (approx. 530 g each), wrap in foil and chill for approx. 2 hours
waiting time approx. 2 hours