Rhubarb cordial

Method

1. Make the syrup. Combine the rhubarb, sugar, cardamom (if using) and 250ml water in a saucepan, and bring slowly to a simmer for at least 10 minutes. Allow to stand for 30 minutes or so.
2. Strain the mixture through a sieve lined with cheesecloth and return the resulting syrupy liquid to the pan. Simmer it very gently for another 20 minutes or so until it has thickened noticeably. Allow the syrup to cool completely before diluting to taste with ice and fizzy or still water.