To make the herb broth, place the turmeric, cardamom and coriander seeds in a frying pan and dry fry for two minutes, to release the flavours.
Add the chicken stock and double cream. Bring to the boil, then reduce the heat to simmer for five minutes.
To make the prawns, place the cayenne, paprika, olive oil, lemon juice and cardamom seeds into a bowl and mix well.
Add the prawns and leave to marinate for ten minutes.
Heat a griddle pan until smoking. Add the prawns and chargrill for two minutes each side, or until cooked through, and season with salt and freshly ground black pepper.
To serve, pour the broth into a warm bowl and serve the prawns on top.