Boil a large fish in 2 quarts of water; season with salt and paprica. Add 1 sliced onion, 2 leeks cut fine, 2 sprigs of parsley and 1 bay-leaf. Let cook well; then remove the fish. Add 1 tablespoonful of butter and 1 quart of oysters. Let boil ten minutes. Add 1 cup of hot cream; season to taste and serve very hot.