For the potato salad, wash the potatoes and cook covered for approx. 20 minutes (depending on size). Rinse, peel and let the potatoes cool.
Peel and chop 2 onions and sauté them in hot oil in a pan. Stir in vinegar, mustard, 200 ml water and stock. Bring to the boil briefly. Season with salt and pepper.
Slice the potatoes and place in a bowl. Mix with the hot broth and let steep for at least 30 minutes. Wash the chives, shake dry and cut into rolls. Fold under the potatoes.
For the tartar sauce, boil 2 eggs hard, quench, peel and let cool. Wash parsley and dill, shake dry and finely chop. Peel 1 onion, chop very finely. Also chop the boiled eggs and gherkins as small as possible. Mix everything together with the mayonnaise, season with salt and pepper.
For the fried fish, whisk 2 eggs in a deep plate. Place the flour and breadcrumbs separately in deep plates. Wash the fish, pat dry, cut into 4 pieces and season with salt and pepper. Turn one after the other in the flour, egg and breadcrumbs. Heat the clarified butter in a pan and bake the fish until golden brown on both sides.
Arrange the fried fish, potato salad and tartar sauce on plates. Garnish with lettuce and lemon.