Heat a frying pan over medium high heat, and add the coconut oil.
Add the prawn/shrimp heads to the pan if using.
Cook the prawn/shrimp heads for about 5 -10 minutes until the heads become crispy and caramelized. If not using the heads proceed to the next step.
Add the onion, ginger, garlic, a generous pinch of salt and reduce the heat to medium and cook the shrimp heads until they soften - a few minutes.
Add the curry powder, fennel powder, paprika, cayenne pepper, black pepper, curry leaves and stir frequently for about 5 minutes, until the spices are fragrant and have formed a paste with the onion, garlic and ginger.
Add the coconut milk, 2/3 cup water, fresh red chili pepper, lime juice and stir to combine. Bring to a boil.
Cover and simmer for about 10 - 15 minutes until the mixture is thick.
Add the peeled prawns/shrimp into the curry base and gently mix to combine and completely coat the prawn/shrimp with the sauce. Add a bit of water if the sauce is too thick, or you would like more sauce.
While stirring, bring the mix to a boil. Cook for an additional 10 minutes, or just until the prawns/shrimp is cooked through and is pink. Season with salt to taste.
Turn off the heat and cover the pan with a lid and let the prawns/shrimp sit in the sauce for a few minutes.
Sprinkle cilantro to garnish if using, and serve with steamed Basamati rice . Enjoy!