This dessert is an easy-to-make ‘mousse’. You can make it in a couple of minutes using a food processor, but it will require a few hours in the fridge to cool and become firm. Use berries that are full of favour to make the purée. About 500 g (1 lb) of assorted berries will yield 350 ml (12 fl oz) of purée. I used equal quantities of strawberries and raspberries.