1 tablespoon water
600 ml (1 pint) sparkling mineral water
750 ml (1 1/4 pints) bottle sparkling dry white wine
2 tablespoons creme de cassis
2. Cool, then combine with the other ingredients and put in an airtight container. Refrigerate overnight.
3. Strain the cup before serving.
The strained cup can be poured into a chilled vacuum flask for a picnic. As an alternative to the creme de cassis, try creme de framboise.