Foto: Kurt-Michael Westermann
Warm up about 2 tablespoons of milk to drinking temperature and dissolve the yeast in it. Stir in a little flour to create a thick-pasted pre-dough. Sprinkle with flour, cover with a cloth and leave to rise in a warm place (28–30 °C) for about 15 minutes, until the surface begins to show small cracks.
Use the rest of the milk and stir together the egg, egg yolks, salt, icing sugar, vanilla sugar, grated lemon rind and rum. Add the melted butter and beat. Using a blender with a kneading hook, blend the mass with the remaining flour and the yeast dough until smooth. Cover with a cloth and leave to rise at room temperature for about 1 hour.
Knead the dough again and on a floured surface shape into a roll. Cut nut-size pieces about 20 g in weight and, using the palm of your hand, shape into round balls. Dust with flour and press them a little with a baking tray. Place on a baking tray and leave to rise in a warm place.
Heat some oil (160 °C) in a pan for deep frying or in a saucepan and fry a golden brown on both sides. Scoop out and place on a cake grid to drain. Fill a pastry bag with the rum-jam mix and squeeze into the doughnuts. Dust with icing sugar.