200 g (7oz) weightwatchers reduced fat thick cream
350 g (12oz) mixed berries
Line a 33cm x 23cm (13in x 9in) Swiss roll tin with baking paper. Pre-heat the oven to 150°C (fan oven 130°C, gas mark 2).
Mix the cornflour, vanilla and vinegar together. Combine the cocoa and water in a separate bowl. Whisk the egg whites into soft peaks, then whisk in the sugar 1 teaspoon at a time. Whisk in the cornflour. Fold in the cocoa.
Spoon into the tin and bake for 45–50 minutes. Turn out onto a large sheet of baking paper. Remove the lining paper. Cool. Spread with the cream and scatter over the berries. Roll up and sift over a little cocoa to serve.