To clean the cockles properly, leave them under cold running water for about 15 minutes, agitating them every so often to get rid of any sand. Check over the gurnard fillets for pin bones, removing any you find with tweezers.
Put the shallots in a pan with the white wine and bring to the boil. Add the cockles and parsley, season lightly and cover with a tight-fitting lid. Cook over a hi