Preparation time: less than 30 mins, Cooking time: 30 mins to 1 hour, Serves: Makes about 450ml/16fl oz (1-2 jam jars)
300g/10½oz fresh blackcurrants
300g/10½oz granulated or caster sugar
1 small lemon, juice only
Pick all the stalks from the blackcurrants, place the fruit in a saucepan, cover with 250ml/9fl oz water and bring it to the boil. Simmer for 20 minutes, or until the skins of the currants are very tender and the liquid gets almost evaporated.
Add the sugar and lemon juice, bring it to boil, then cook until the mixture reaches 105C/220F on a sugar thermometer.
Leave it to cool for a few minutes, then pour into hot, clean jars and seal immediately.