Wash the potatoes and cook covered for about 20 minutes. Quench, peel and let cool down a little
Wash the fish fillet, dab dry and cut into 8 pieces. Sprinkle with lemon juice and let it steep a little
Wash the marjoram and, except for something to garnish, chop coarsely. Crush the peppercorns in a mortar. Clean, wash and cut the leek into rings. Steam in 2-3 tablespoons of hot fat in a large pot for about 5 minutes. Season with salt and pepper
Sprinkle with 1 tbsp. flour and sauté. Stir in just under 1/2 l water, milk, marjoram and stock. Bring to the boil and simmer for about 5 minutes
Season fish with salt and dust with 1 tablespoon of flour. Fry in hot oil in a coated pan for about 2 minutes on each side. Sprinkle each side with crushed pepper and fry for a further 5 minutes, turning
Cut the potatoes into slices. Add to the leek and heat. Season to taste with salt and pepper. Arrange everything and garnish with rest of marjoram