First, sift the flour into a suitable bowl, mix with the salt and make a well in the center. Add the egg, lukewarm water and pepper. Knead the dough with your hands. Remove the dough from the bowl and knead it properly on the floured work surface. Shape dough into a ball, divide into 4 portions and wrap in plastic wrap.
Heat butter in a frying pan. Sauté the onion in it, add the garlic, mix with the beef mince and fry until crumbly. Season with salt and pepper and fold in the sour cream.
Mix the egg with the whipped cream.
Roll out the dough pieces round and very thin, cut out circles of about 6 cm ø with a glass. Place about 1 tsp of filling in the center of each circle and brush the edge with the egg-cream mixture. Fold into a semicircle, closing the edges well with your fingers. Work the whole dough and filling in this way.
Place pierogi in batches in a large saucepan of boiling vegetable soup and cook for about 3-4 minutes until they float to the surface of the water. Lift out.
Finely chop parsley. Peel and finely chop onion. Cut bacon into fine strips. Fry bacon in a pan without further fat, add onion and parsley.
Serve pierogi z mięsem with the onion-bacon mixture (and possibly some soup).