Peel and finely chop the onions. Rinse and drain the shrimps
Melt the crab butter in a large pot (add the crab paste only at the end). Fry the onions in it. Dust with flour and sweat it. Add 1 1/4 l water, fish stock and 250 g cream while stirring. Bring to the boil and stir in the stock. Let simmer for about 5 minutes
Wash the dill and cut it finely. Season soup with salt, pepper, sugar and cognac. Add shrimps and heat in the soup. Beat 125 g cream until half stiff. Pour as a blob on the soup and sprinkle with dill