Put in a food processor and pulse until finely chopped (but not blitzed to a purée). Heat the sugar and vinegar gently in a pan until the sugar dissolves. Add the pepper mix and boil for 15 minutes. Drop a spoonful on to one of the frozen plates, wait for 30 seconds then run your finger through it. If it wrinkles it has reached the setting point. If it doesn’t, cook the mixture for 5 more minutes, then repeat the test. Take the jam off the heat, then pour into the sterilised jars and leave to cool before adding the lids. They will keep, unopened, for 2 months in a cool dark place, or a month in the fridge once opened.