Blackberry Sauce

• 6lb/3 kg blackberries
• 1 pint/500

Clean blackberries and remove stems and unripe berries. Put into a pan with just enough water to cover and simmer until the berries are soft. Strain through a sieve, and put the purée into a pan with the remaining ingredients. Simmer for 15 minutes, put into hot bottles and seal. Sterilize for 30 minutes in a water bath.