Put all the ingredients, except the orange zest and juice and the cranberries, into a heavy-based pan and bring to a simmer over a medium heat. Cook, stirring often, for 30 mins until the onions have softened, the sugar has melted, and the mixture looks thick and syrupy.

Stir in the orange zest and juice and the cranberries, then simmer for 20 mins more until the mixture has thickened, the cranberries have popped and everything is sticky and jammy. Divide between four small sterilised jars (see tip, below) and leave to cool before labelling. Leave in a cool, dark place for two weeks before opening. Once opened, store in the fridge.