- Place cranberries, onions and water in a saucepan and bring to the boil.
- Turn down the heat and simmer for 5 to 10 minutes until cranberries burst and onion is tender.
- Transfer to a blender and blend until smooth, then return puree to the pan.
- Add vinegar, sugar, salt, pepper and mixed spice. Heat gently, stirring until sugar has dissolved.
- Simmer for 10 to 15 minutes or until the sauce is thick. Pour into sterilised bottles and seal well.
- Store in a cool, dark place for 3 weeks to mature before eating.