Combine all ingredients in a saucepan over low heat. Simmer gently 1 - 1 1/2 hours, stirring often, until cooked into a sauce-like consistency.
Meanwhile, sterilise jars and lids in boiling water at least 10 minutes. Transfer jars from boiling water to a tea towel covered work surface.
Ladle the hot sauce into the hot jars, leaving 5mm headspace at the top. Remove lids from boiling water and seal each jar.
Place a folded tea towel in the bottom of a stockpot or large saucepan. Add the hot jars, lids up, and pour in hot water from the kettle to 3/4 of the way up the jars. Cover and boil 10 minutes. Remove jars and let cool.
Store jars in a dark, dry place. Once opened, keep in the fridge and consume within a week.