Put the flour in a bowl, make a depression in the middle and crumble the yeast. Add 1 tablespoon of sugar. Heat the milk, pour about 1/3 of it into the hollow to form the yeast and mix it with some flour from the edge to form a pre-dough.
Cover and leave to rise in a warm place for about 10 minutes.
Wash the lemon thoroughly, dab dry and finely grate the peel. Dice fat. Add egg, fat, rest milk, 45 g sugar and lemon peel to the pre-dough. Knead well with the dough hooks of the hand mixer for 3-4 minutes.
Cover and leave to rise in a warm place for about 30 minutes.
Place the dough on a well floured work surface, knead briefly once again and roll out to a thickness of approx. 1 cm. Cut out donuts with a donut cutter (approx. 5 cm Ø). Place on a floured baking tray.
Knead the rest of the dough again and again, roll out and cut out until the dough is used up. Cover the donuts and let them rise for 5-10 minutes.
Heat the oil in a high pot to approx. 150 °C. Carefully place donuts in the hot oil in portions and fry for 1-2 minutes until golden brown, turning them over. Lift out with a skimmer, drip off on kitchen paper and allow to cool.
Turn some donuts still hot in 50 g sugar and let them cool down.
Coarsely chop the chocolate coating and melt separately over a warm water bath. Squeeze 1/2 lemon. Mix icing sugar and approx. 1 tbsp. lemon juice to a smooth, thick glaze. Decorate some donuts with icing and pink sugar crumbles.
Dip the rest in dark chocolate, decorate with white chocolate or sprinkle with golden-white sugar pearls. Leave to dry.