The Water caldrop is a seed fruit of the Asian water plant Trapa bicornis.
Under the hard, brown/black skin is white flesh. Boil and peel to bring out the fruit. The water caltrop has the texture of a Brazil nut and the flavour of chestnut.
Boil the water horn chestnuts in water for about 15 minutes, or roast them like chestnuts. Then slice open with the flat side of a cleaver
Water caltrop - 菱角