Watermelon and strawberry crush

Method

1. The day before the picnic, put the fruit and lime juice in a liquidiser and whizz to a purée (you may need to do this in batches).
2. Pour the purée into a large jug and stir in the sugar and lemon verbena or thyme. Leave for 20 minutes, stirring occasionally, until the sugar is dissolved.
3. Pour into clean plastic bottles, leaving space for expansion, and freeze until solid. Use as ice packs for your picnic and it will melt down to a refreshing slushy consistency by the time you eat.
4. Pour the crush into glasses up to about halfway up, then top up with lemonade and serve.