Peel, wash and quarter the potatoes. Cook in 750 ml boiling salted water for about 25 minutes. In the meantime wash, quarter and core apples. Cut the fruit flesh into fine slices and sprinkle with lemon juice. Melt the fat. Fry the apple slices and crab flesh in it. Mash potatoes in the liquid.
Refine with 100 g whipped cream. Add the prepared apple-crab mixture. Season to taste with salt, pepper and horseradish. Lightly whip 150 g cream. Serve the soup in portions with 1 dollop of cream each. Serve sprinkled with marjoram leaves and pepper