Peel and wash the potatoes, cover and cook in boiling salted water for about 20 minutes. In the meantime peel onions. Finely dice onions and bacon. Spread the bacon on 2 large, coated pans and leave them crispy without fat.
Add diced onion and fry until brown. Halve the lemon and squeeze 1 half. Wash the plaice thoroughly, dab dry, sprinkle with lemon juice and season with salt and pepper. Remove bacon and onions and put aside.
Put the flour on a plate, turn the clods in it and tap off any excess flour. Spread 30 g butter on the 2 pans and heat. First fry the plaice on the white side for about 4 minutes until golden brown, then carefully turn and fry for 4 minutes on the other side.
Shortly before the end of the cooking time, add the bacon and onions to the plaice and warm them up. In the meantime wash parsley, dab dry and chop very finely, except for a little bit for garnishing. Drain the potatoes and let them steam briefly on the switched off hotplate.
First melt 20 g butter in it, then add chopped parsley and toss. Cut the remaining 1/2 lemon into slices. Arrange plaice, bacon, onions and potatoes. Garnish with lemon wedges and parsley.