If using frozen berries, thaw in a medium bowl at room temperature for 1 hour; drain.
Blend thawed berries, tofu, Natvia and juice, until as smooth as possible, using a high-powered blender if available; this type of blender will produce a very smooth consistency. Pour mixture evenly among four ¾ cup (180ml) glasses or jars.
Refrigerate for 4 hours or until firm. Top with extra berries before serving.
Cover with plastic wrap and store in the fridge for up to 4 days. If you like serve frozen in glasses, topped with frozen raspberries and blueberries, with raspberries on the stem, for a refreshing fruit fix.