Stroganoff Sauce

• 1 medium-sized onion
• 1 oz (25 g) butter
• 4

Peel and finely chop the onion. Melt the butter in a frying pan over low heat, add the onion and fry gently for 5 minutes to soften but not brown. Meanwhile, trim and slice the mushrooms.

Add the mushrooms to the pan and toss them over the heat for a few minutes. Stir in the tomato purée and soured cream. Bring just to the boil (soured cream does not separate) and season with salt and p