Clean, wash and cut the leek into rings. Peel 2 oranges so that the white skin is completely removed. Cut oranges into slices. Squeeze 2 oranges. Heat 20 g butter in a saucepan and sauté the leeks for 4-5 minutes, turning them over. Season with salt and pepper. Pour in orange juice (approx. 150 ml), bring to the boil and distribute in 4 ovenproof dishes
Wash the salmon fillet, dab dry and cut into 4 pieces. Season with salt, place on the leek in the moulds and cover with the orange slices. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-25 minutes
Peel horseradish, grate finely (8-10 g) and mix with 25 g of softened butter. About 5 minutes before the end of the cooking time, spread horseradish butter on the salmon and bake with it