Heat the oil in a frying pan over a moderate heat until just rippling.
NOW! BE VERY CAREFUL - HERBS SPLATTER LIKE FIREWORKS SO DO THIS NEXT STAGE WITH CAUTION!
In small batches, add the herbs to the oil. They'll splatter violently then begin to sizzle. Let them sizzle for 10-20 seconds then remove to a waiting paper towel. Repeat with all the herbs. Set aside.
How to make the green masala paste
Using a stick blender or food processor, blend into a paste the herbs, curry leaves, chillies and coconut milk. Set aside.
How to make the curry
Heat the coconut oil in a wok over a moderate heat until hot.
Add the onion/shallots and fry them for about 2-3 minutes until soft.
Add the garlic and ginger and fry for 1 minute before adding the ground cumin, coriander and cardamom. Let this sizzle for 30 seconds before adding the shrimp. Season generously with salt & pepper.
Stir fry the shrimp for 1-2 minutes until pink.
Add the green masala paste and stir well. Let it come to a boil then pour in the coconut milk and the same amount (1 cup) of water.
Bring this to a boil and let it bubble merrily for 5 minutes to cook the prawns through.
Remove from the heat. Scatter over the crisp fried herbs and squeeze over the lime. That's it!
Serve with plenty of fluffy basmati rice to soak up the utterly delicious sauce.