Makes approximately 850ml 1kg blueberries 150g caster sugar Place the blueberries in a large saucepan and cover with 300ml of cold water. Bring to the boil, stirring occasionally, then simmer for 4-5 mins until a pulp. Allow to cool, then strain into a large bowl through a sieve. Leave to strain for 1 hr, pushing the fruit through with the back of a spoon from time to time. Discard the pulp, or freeze to use in another recipe. Transfer the liquid to a separate saucepan and add the sugar. Simmer for 5 mins, so the sugar has dissolved completely. Boil for 4 mins, until glossy and slightly thickened. Using a sterilised* jug, pour into a sterilised bottle. Seal with a sterilised top, and store in the fridge. Use within three months, and within a week once opened. Water down, approximately 1 tbsp to 150ml of cold water, to taste, before drinking. *To sterilise, wash items in hot, soapy water, then rinse and dry. Fill with boiling water for 2 mins, then discard the water and dry.