Boil the potatoes until soft, press them into a smooth puree, mix with all-purpose flour and egg, season with salt and white pepper, and knead with water into a smooth, non-sticky dough. Mix the bryndza with the egg and sautéed onion. Roll the dough out into a thin sheet, from which we cut circles with a diameter of 80mm using a cutter. In the center of each circle, place a dollop of the bryndza filling, fold in half, and press the edges firmly so that the filling does not leak during cooking. Arrange the pierogi on a greased perforated tray and cook in a combi steamer. After cooking, toss with the fat rendered from the bacon and serve on a plate with sour cream and crispy bacon.