Left over crab shells should never be thrown out as they can be used to form the classic French base for soups: bisque.
Shell from 2 crabs
2 carrots chopped
½ leek chopped
½ Spanish onion chopped
Small bunch of thyme
2 bay leaves
75ml dry white wine
4 table spoons tomato puree
1.5 litre fish stock
100ml double cream
Salt and pepper to taste
1. Put the crab pieces in to the pot and break them up a bit more with a rolling pin. Heat up the crab shells for 5 minutes with some olive oil and then add the white wine.
2. Add the onion, leek, garlic, carrots, thyme and bay leaf. Cook off until the vegetables begin to colour and the liquid has evaporated.
3. Add the tomato puree and fish stock to the pan. Bring to the boil and simmer for 45 minutes.
4. Press as much liquid out of the shells and vegetables with the back of the ladle and discard everything left in the sieve.
Strain the soup once more through a fine sieve to remove all finer pieces of shell. Bring back to the boil and reduce a little to concentrate the crab flavour. Add some double cream and season to taste.