Mix flour, 1 pinch of salt and 30 g sugar in a large bowl. Add 1 egg and 50 g butter in flakes. Warm the milk lukewarm, crumble yeast into it and dissolve it while stirring. Pour onto the flour mixture and knead with the dough hooks of the hand mixer for 4-5 minutes to a smooth dough. Cover and leave to rise in a warm place for about 45 minutes
Peel the onion and cut into small cubes. Dice the bacon finely as well. Heat 1 tablespoon butter in a pan, sauté onion and add bacon. Fry for about 3 minutes. Remove from the heat and let it cool down
Knead the yeast dough again briefly and divide it into 4 equal pieces. Form into rolls with your hands on a lightly floured work surface and divide each roll into 4 pieces of the same size. Form into balls and roll out round (approx. 14 cm Ø). Spread approx. 1 tbsp. bacon and onions evenly on each circle, leaving a rim of approx. 1 cm free.
Fold half circles to semicircles. Press the edges together with a fork. Put them on 2 baking trays lined with baking paper and let them rise again for about 15 minutes. Whisk 1 egg, 1 pinch of salt and sugar and spread a thin layer on the dumplings. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ see manufacturer) one after the other for about 20 minutes. Take out and serve while still warm
Waiting time approx. 1 hour