Marinate the prawns with the garam masala and some salt and refrigerate for half an hour
Heat 2 tablespoons of oil in a pan and flash fry the prawns, just to brown them a little for a few seconds. Cover with foil and set aside
Clean any masala that's left in the pan, otherwise it will burn. Add another tablespoon of oil and fry the bay leaf and cinnamon stick until fragrant
Add the onion and curry leaf and sauté the onion until its slightly brown
Add the ginger/garlic paste and cook for a minute
Add the masala, coriander and turmeric and cook for at least 2 minutes on low heat. Add a drop of water if required
Add the coconut milk and simmer for at least half an hour until the sauce starts to thicken
Add the tamarind and sugar. Cook for 5 minutes. Remove the bay leaf, curry leaf and cinnamon stick and blend the sauce until it's smooth and creamy
Add the prawns and heat through. Season with more salt if required