1. Cook the tapioca in water until tender, adding more if necessary. Remove from the heat.
2. While still hot, stir in the coconut cream until melted and sweeten to taste. Add more water or coconut milk to obtain a soupy consistency. Pour into a serving bowl or tureen, or into individual dishes.
3. Peel the mangoes and cut into thin curved slices. When the tapioca is completely cool, arrange the mango on top, and chill until required.