Melt the butter in a saucepan and sweat the flour in it, deglaze with the stock and wine. Bring to the boil and simmer for about 5 minutes, then season with salt and pepper.
Whip the cream until it is half stiff and stir 2/3 of it into the hot soup. Add the crab meat.
Wash and cut the dill. Serve the crab soup garnished with the remaining cream and the dill.