Preheat the oven to 200°C/180°C fan oven/Gas Mark 6. Melt half the butter in a roasting tin or a 2 litre (3 1/2 pint) shallow flameproof dish, then fry the sausages until lightly browned. Lift out and set aside. Gently fry the onions in the remaining butter for 10 to 15 minutes or until soft.

Stir in the remaining ingredients, season, bring to the boil and bubble for 2 minutes or until reduced by half. Place the sausages on top of the onions so they continue to brown when cooking then place the dish, uncovered, in the oven. Cook for about 45 minutes, stirring occasionally. The onions should be soft, golden and glazed with the pan juices - if the juices are too concentrated, stir in 4 tablespoons of boiling water. Garnish with parsley and serve.