Fry the onion until it softens, then add the ginger, garlic and chilli pepper. Cook for a couple of minutes. Add the coriander and dry spices and cook for an additional couple of minutes.
Add the cream, milk, tomatoes and water and cook for around 15 minutes. Reduce the heat and place the fish in the sauce. Continue to heat just long enough for the fish to be cooked, around 5-10 minutes depending on its size and thickness (don't overcook or you will end up with rubbery fish!). Serve immediately with rice and garnish with fresh coriander. Enjoy!