Peel the mango and slice off the flesh from the stone. Roughly chop the flesh. Peel the tough outer leaves from the lemon grass and discard. Finely chop the more tender stem. Crush the cardamom pods and discard the papery husks. Reserve the black seeds.
Place the mango flesh, chopped lemon grass and cardamom seeds into a blender. Add 250ml iced water. Blitz till smooth. Add more water if needed or a good dollop of yogurt.
Ripe and ready If your mango is a little firm when you unpack it, pop it in a paper bag with the free banana we've sent you. It will help the mango ripen, and you can also add it to the lassi (this will affect the nutritional content).