In a spice grinder grind the chilies, turmeric and lemon grass. In a bowl mix together the garlic and ginger puree and the ground spices to form a paste.
Heat the oil in a pan and add the spice paste, heat the paste for a minute or so until aromatic. Add the milk and bring to the boil, reduce heat to a simmer and add the fish fillets.
Simmer for 15 mins or until the fish is cooked through and flakes easily with a fork.
Serve over rice for a low fat meal.
Tip
Frozen fish fillets can be used as a convenient and cheaper alternative to fresh.