- Simmer the water, sugar and lemon zest in a small saucepan over a medium heat for a few minutes until the sugar has melted and syrup has thickened slightly.
- Reduce heat, then add blackcurrants and lemon juice and simmer for a few minutes until blackcurrant skins have burst.
- Remove from heat, add creme de cassis if using, taste and add a little more sugar if required.
- Serve at room temperature, stirred through natural yoghurt or as a topping for icecream.