Stuffed Fillets of Plaice with Courgettes

• 1 onion, finely chopped butter for frying
• 175 g/6 oz mushrooms, finely chopped

Start with the mushroom farce: soften the onion over moderate heat in about 1 tablespoon of butter. When the onion is transparent looking add the chopped mushrooms and fry until you have a soft, reduced mixture. Tip this into a bowl and allow to cool.

Set the oven to moderately hot (200°C, 400°F, Gas Mark 6). Season the mushroom mixture well with salt and pepper and divide it between th