Tip half the cranberries, the ginger and chillies into a food processor and whizz until very finely chopped. Scrape into a heavy-bottomed pan and add the remaining cranberries along with the sugar and vinegar, then bring everything to the boil, skimming off any scum that comes to the surface. Turn the heat down to a gentle simmer and keep cooking for about 20-30 mins, stirring occasionally.

Once the jam is starting to become sticky, continue cooking for a further 5 mins, stirring frequently so that the mixture doesn’t burn on the bottom of the pan. It should look like a thick, bubbling lava. Cool slightly, then transfer to sterilised jars and leave to cool completely. Will keep for three months in a cool, dark place; keep in the fridge once opened.