Toss prawns with lemon juice and marinate in a shallow dish.
Heat 30ml oil in a pan and cook onions for 3 minutes until soft.
Add turmeric, cardamom, and chilli powder then cook for 2 minutes.
Stir in remaining oil, cinnamon, garlic, and ginger and cook for 2 minutes.
Blend coriander with 175ml coconut cream in a food processor, reserving some sprigs.
Stir coconut mixture into the pan and bring to a boil.
Simmer gently for 2 minutes and then stir in marinated prawns and salt.
Cook for 2 minutes until prawns are tender and garnish with coriander.