For the sauce: Put the oil in a large pot with the onion and garlic. Saute over high heat, stirring with a wooden spoon, until the onion and garlic are soft, then add the coriander, cumin, curry powder and thyme. Mix until the spices start to stick to the pot, 3 to 4 minutes. Add the mango and mix until the spices loosen from the bottom of the pot, then add the tamarind juice and coconut milk. Lower the heat to medium-high and cook about 5 to 10 minutes, then add the salt and pepper and turn the heat down to medium. Cook for about 25 minutes, stirring occasionally. When the sauce has reduced by 25 percent, it¿s ready; transfer it to a bowl and set it aside.
For the marinade: Place all of the ingredients, except for the oil, in a food processor. With the processor running, add the oil slowly until the mixture forms a paste. Transfer the marinade to a large bowl. Cut the mahi mahi into 6-inch portions and then rub each piece of fish with marinade until well coated. Take a banana leaf and lay it flat, then wipe it with a wet, warm towel. Lay a piece of fish on top of the leaf and fold the leaf over it. Repeat with the remaining leaves and fish. Chill the wrapped fish pieces in the refrigerator for 2 hours, then steam them in a steamer until the fish and juices turn white, 10 to 15 minutes. Cut each piece in half, leaving it in the leaf, and pour the sauce over each serving. Serve with rice or any other starch.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.