Vermouth and Tomato Sauce

• ½ pint/285 ml red vermouth
• 2 medium onions, skinned and chopped very finely

Put the vermouth and finely chopped onions into a saucepan and simmer gently till the onions are very soft and the vermouth is reduced almost to nothing. Melt the butter in another saucepan, and stir in the flour, let it cook for a minute or two, then stir in the milk, stirring all the time till the sauce boils. Simmer for a minute, then take the pan off the heat, and season to taste with peppe