Put flour into a bowl and create a well in the middle. Dissolve yeast in milk, then pour into well and dust with some flour. Cover and let rise for 15 minutes. Knead in eggs, sugar and oil, then cover and let rise again for 30 minutes.
Peel and chop onion and garlic. Heat butter and oil in a pan and cook onion and garlic. Add meat and cook until crumbly. Add sauerkraut and season with salt and pepper.
Roll out dough on a floured surface and add mounds of about 1 tablespoon of meat mixture to half of the dough, about 8 cm (approximately 3 inches) apart, each. Brush egg whites between mounds, then fold over remaining dough and press between mounds. Ct mounds apart and place on a greased baking sheet. Brush with beaten egg yolk and bake in an oven preheated to 250°C (approximately 475°F) for about 20 minutes. Remove, let rest briefly and serve.