Warm up the milk. Melt butter in it. Mix 400 g flour, yeast, sugar and 1 pinch of salt. Add egg and egg yolk. Add warm milk-butter mixture. Knead the dough first with the dough hooks of the mixer, then with your hands for 5-6 minutes to a smooth dough.
Form the dough into a ball and put it back into the bowl. Cover and leave to rise for approx. 1 1⁄2 hours in a warm place. Knead the dough again with your hands. Then let it rest in the fridge for at least 3 hours.
Knead dough briefly. Roll out to a thickness of approx. 1 1⁄2 cm on some flour. Donut cutter (approx. 8 cm Ø; various sizes at e.g. amazon.de from 6 € plus shipping, alternatively cut out the outer circle e.g. with a glass.
For the hole in the middle, use the bottom edge of a syringe nozzle. So that nothing sticks, dip both briefly in flour) briefly in flour. Cut out a total of 13-15 dough rings, kneading, rolling out and cutting out the dough again and again.
Place the dough rings with a little distance between them on a sheet of baking paper sprinkled with flour. Dust lightly with flour, cover with a clean tea towel and leave to rise in a warm place for about 1 hour.
Heat the oil in a deep fryer or in a wide pot to 180 °C (use a frying thermometer! Alternatively, hold a wooden skewer in the fat - if bubbles rise from it, it is hot enough). Fry 3-4 donuts for approx. 1 1⁄2 minute each, turning once.
Drain on kitchen paper. Decorate according to the recipe.
For Verry Berry, knead 200 g dried cranberries into the yeast dough, then let it rise.
For Girly-Swirly, stir 250 g icing sugar with approx. 2 tablespoons of water until smooth. Melt 25 g dark chocolate. Spread donuts with icing. Immediately sprinkle chocolate over them and spoil.
For Sugar Babe, roll the deep-fried donuts, still warm, in approx. 100 g sugar and allow to cool.
For The Pink Ring, thaw 35 g frozen raspberries and crush with a spoon. Mix with 175 g icing sugar to a glaze. Dip the donuts half into the icing. Leave to dry.
For Dark and Nutty, melt 250 g of dark chocolate, dip donuts half in each and let them drain briefly. Sprinkle with 2 tablespoons of toasted almond flakes. Leave to dry.