Gently warm milk with butter, vanilla sugar and lemon flavor (e.g. in a microwave).
Now put the flour in a bowl and make a well in the middle. Put the yeast, 1/2 teaspoon sugar and 1 tablespoon lukewarm water in this hollow and make a pre-dough with a little flour from the edge. Let it rise for about 10 to 15 minutes.
Now add the egg, 65 g sugar, 1/2 teaspoon salt and the warmed milk mixture and knead everything into a dough until it loosens from the edge of the bowl. If necessary, add water drop by drop. Now shape the dough into a ball and cover it and let it rise in a warm place for about 1 hour.
Knead the dough again and roll out approx. 2.5 to 3 cm thick. Now cut out circles with a glass. For the hole in the middle, remove the batter with a small shot glass. Place the donut blanks on a prepared baking sheet and let rise, covered, for another 15 to 20 minutes.
Heat a deep fryer to approx. 170 ° C and fry the donuts in portions for approx. 2 minutes on each side (the frying basket is not required). Lift the baked donuts out of the oil with a slotted spoon and let them drain on kitchen paper.
Now melt the chocolate in a water bath. Finally, dip one side of each donut in it.