Chicken Bake With Yogurt Topping

15 g/1/2 oz polyunsaturated margarine
1 small onion, peeled and finely chopped
2 celery stalks, finely chopped
100 g/4 or button mushrooms
350 g/12 oz cooked chicken, finely chopped
1 tablespoon chopped parsley
salt
freshly ground white pepper
'Topping:
300 ml/1/2 pint plain low-fat yogurt
2 egg yolks
1 teaspoon prepared mustard

Melt the margarine in a pan. Add the onion, celery and mushrooms and fry gently for 5 minutes,

stirring frequently. Add the chicken, parsley and salt and pepper to taste. Transfer the mixture to a casserole and press down firmly.

To make the topping: put the yogurt in a bowl with the egg yolks, mustard and salt and pepper to taste. Mix and then pour over the chicken.

Bake in a preheated moderately hot oven (190 °C/375 °F, Gas Mark 5) for 25 minutes. Serve immediately while hot.

SERVES 4