Soak the mussels in cold salted water with a little flour or oatmeal thrown in, for an hour or longer if there is time. The mussels eat the flour or oatmeal and clean themselves. Scrub the mud off the mussels and pull off the seaweed-like beard’ on them. Tap any that are open, if they do not close they should be discarded. Rinse the mussels thoroughly. Put them in a large pan in about 1 in (2.5 cm) of boiling water. Cover the pan with a lid and steam the mussels open which will take 1–3 minutes. Remove the mussels from their shells and arrange them in a large, fairly shallow ovenproof (earthenware looks best for this) dish. Make up about 1¼ pints (720 ml) fairly thick white sauce, season it with salt and pepper and stir into it as it simmers the grated cheese – not the Parmesan – the crushed garlic, the turmeric and the sherry. When the cheese has melted and the sauce is smooth pour it all over the mussels. Dot with butter and sprinkle with Parmesan cheese. Cook in the centre of a pre-heated oven at Gas 3 (325°F/160°C) for 30–45 minutes. To make it look extra good sprinkle some bright green chopped parsley round the edges of the dish before serving.