Cook the rice in about 100 ml boiling salted water for about 20 minutes. Wash lemon hot, dab dry and cut off 2 thin slices. Squeeze the rest of the lemon (approx. 1 tablespoon juice). Wash the fish and pat dry. Heat the oil.
Fry the fish for about 8 minutes while turning. Season with salt and pepper. Take out and keep warm. Cut leek into strips. Steam in little boiling salt water for about 4 minutes. Fry the lemon slices briefly in the frying fat and take them out. Deglaze frying fat with milk, bring to the boil. Add lemon juice. Thicken sauce. Season to taste with salt and pepper.
Deglaze frying fat with milk, bring to the boil. Add lemon juice. Thicken sauce. Season to taste with salt and pepper. Add fish and lemon slices to the sauce, heat up briefly. Drain rice and leek if necessary. Arrange everything and garnish with parsley and lemon peel if necessary