Peel, wash and halve the potatoes. Fry in hot oil for about 15 minutes at medium heat. Season with salt and pepper. In the meantime wash salmon and pat dry. Sprinkle with some lemon juice and season with salt.
Fry in melted butter over medium heat for about 5 minutes, turning. For the sauce, briefly bring cream and stock to the boil. Stir in horseradish. Season to taste with salt, pepper and a few drops of lemon juice.
Stir in the sauce thickener, bring to the boil again. Shortly before serving, whip up with the cutting stick until foamy. For the salad, peel onions and cut into fine slices. Clean, wash and drain the lamb's lettuce.
Peel the orange so that the white skin is completely removed. Cut out the fillets between the parting skins. Mix onions, lamb's lettuce and orange fillets and drizzle with lime juice. Cut beetroot into fine strips and fold in carefully.
Serve fish, potatoes, sauce and salad in portions, garnish with lime and lemon slices.