The shells from prawns, langoustines or crayfish form the base for a truly great soup, especially those from langoustines. It's really worth saving them, as langoustines especially cost such a lot in the first place, and it's a shame if the shells end up in the bin.
A good knob of butter
500g-1kg cooked shrimps or langoustines or crayfish, shelled, or just about 500g of shells
1 medium onion, peeled and roughly chopped
1 leek, roughly chopped and washed
3 cloves of garlic, peeled and roughly chopped
1tsp fennel seeds
A good pinch of saffron
1 bay leaf
A few sprigs of thyme
1tbsp tomato purée
100ml white wine
80g pudding rice
2 litres fish stock (made from good cubes is fine)
100ml double cream, to finish
Salt and freshly ground black pepper
Melt the butter in a large thick-bottomed pan and gently cook the shells, onion, leek, garlic, fennel seeds, saffron, bay leaf and thyme for 4-5 minutes with a lid on, stirring every so often.
Add the tomato purée, white wine, pudding rice and fish stock, season and bring to the boil.
Simmer very gently for 1 hour then blend in a liquidiser until smooth and strain through a fine sieve.
Re-season if necessary, add the double cream and simmer for another minute.
You can serve this dish with some chopped or whole prawns or langoustines and a chopped herb such as tarragon, parsley or chervil.