Cut the pomelo in half and scoop out the segments and juice. Discard the pith and thick skin surrounding each segment and break the flesh into small pieces. Stir the peanuts into the pomelo flesh. Set aside to allow the flavours to blend.
Bring a saucepan of water to the boil and simmer the prawns for 1—2 minutes or until they turn pink and are cooked through. Remove them with a slotted spoon and drain well.
Finely shred the spring onions and mint leaves. Add the prawns to the pomelo flesh with the grapefruit juice, fish sauce, spring onions and mint.
Sprinkle the red chilli, crushed chilli or pepper and nutmeg over the salad and toss together. Line the inside of a bowl with salad leaves and spoon in the prawn and pomelo mixture. Serve immediately.