Heat 3 1/2 tablespoons mustard oil in a small nonstick pan over a medium heat until smoking. Remove the pan from the heat, and set aside for 20 to 30 seconds.
Add the cardamom pods, cloves, bay leaves, and panch phoran, and fry over a low heat, stirring well, until the mixture starts to darken in color.
Add the onion, and fry for 2 to 3 minutes, or until softened. Add the green chiles, ginger paste, and garlic paste, and continue to cook, stirring well, for another minute.
Add the coriander, cumin, turmeric, chile powder, paprika, if using, and salt, to taste, and stir well to combine, and then add the water. Bring the mixture to a boil, and then turn down the heat and simmer the mixture for 12 to 15 minutes, or until the volume of liquid has reduced. Set aside.
Meanwhile, heat the remaining 1 1/2 tablespoons oil in a separate frying pan over a high heat, add the sea bream pieces, and fry for 1 to 2 minutes, turning once, until the fish pieces are golden brown on all sides. Add the fish to the spice mixture, adding more water as necessary to thin the sauce. Bring the mixture to a simmer, and cook for another 3 to 4 minutes. Serve immediately with basmati rice.
*Can be found at specialty Asian markets. **A blend of equal quantities of fenugreek, nigella seeds, fennel seeds, cumin and mustard seeds, available from Asian supermarkets, also known as Bengali five-spice. Using fish heads in your curry will really enhance the flavor. If you find them offensive at the table, just leave them in the cooking pot and serve the rest of the fish.