Peel and wash the potatoes and cook them in salted water for about 20 minutes. Peel the onions. Chop onions and bacon finely. Skip the bacon in a large pan. Add diced onions and fry until brown. Take out the bacon-onion mixture and put half of the bacon fat in a second large pan.
Wash the plaice thoroughly and dab dry. Sprinkle with lemon juice and season with salt and pepper. Turn in the flour, knock off excess flour.
Put 1 tablespoon of butter in each pan and heat it up. First fry 1 plaice on the white side for about 4 minutes, then carefully turn it over and fry it on the other side for 4 minutes. Add half of the bacon mixture to each plaice and heat up briefly.
Wash parsley, dab dry and chop. Drain the potatoes and let them evaporate briefly. Add 2 tablespoons of butter and parsley and toss through. Arrange plaice with bacon mixture and parsley potatoes.