Peel the potatoes and cut into small pieces, finely dice the onion and garlic.
Heat the butter and oil in a large saucepan and sauté the onions and garlic. Add the potatoes, fry briefly and season with salt. Deglaze with wine, fill up with stock and cook covered for approx. 25 minutes. Then puree the soup and strain it through a sieve if necessary.
In the meantime, put the crabs in a bowl and mix with a tablespoon of sour cream and 2 teaspoons of dill and season with a little pepper.
Add the remaining sour cream to the soup, puree it again and then season well with salt, pepper and nutmeg.
Place the crab and sour cream filling in the middle of the preheated plate and carefully spread the soup around it. Garnish with a little dill if necessary.