Add garlic, Kashmiri red chilli, turmeric, coriander powder, cardamom, cloves, green chillies, black pepper and 2 tablespoons of water to the small food processor. Grind this to a fine paste and set aside.
Heat oil in a saute pan. Add the mustard seeds, fenugreek seeds, cumin seeds and allow to sizzle for a few seconds. Add the curry leaves, asafetida and sauté for 1 minute on low heat until fragrant.
Add the prepared paste, light coconut milk, tamarind solution, and ¼ cup water to the food processor swirling+ shake to remove the paste still in the jar. Add this to the pan and continue to sauté for 5-7 minutes on low heat until the raw flavor of the spices has mellowed.
Add the fish pieces, regular thick coconut milk and simmer, covered for 7-10 minutes(depending on the thickness of the fillets) or until the fish is fully cooked, gently submerge them in the curry.
Serve with steamed rice, papadum, vegetables or salad.