Mahi mahi is sturdy and meaty, with a texture more akin to a tender chicken breast than a flaky fish. Fillets hold up well to most cooking methods, and steaming is one good option for a tender, tasty meal. As for flavoring, the sky's pretty much the limit with this versatile fish. Use any favorite seafood recipe or come up with something on your own. If you don't own a steaming basket, steam mahi mahi filets in the oven instead.
Steaming frozen mahi mahi won't work well, so use fully defrosted fillets. Otherwise, it cooks unevenly and the texture turns unpleasantly chewy. The best way to thaw the fish fillets is to put them in the refrigerator overnight. If you don't have that much time, and if the fillets are sealed in airtight packaging, immerse the packages completely in cold water for one to two hours. Replace the water with new, colder water every half hour. Avoid defrosting mahi mahi fillets in the microwave; the outside starts to cook before it's thawed through and your fish ends up rubbery.
Steamed mahi mahi fillets support a diverse range of flavorings. Steamed fish is traditional in many East Asian cuisines, so consider flavoring along those lines. For example, brush the fillets with cooking oil and soy sauce or tamari, then add some salt, pepper, chopped scallions and minced ginger. A Thai curry sauce works well, too. Or, try some Cajun blackening seasoning if you want to go a different spicy route. Other simple, tasty options include lemon juice, salt, pepper and dill or, for something with a bit more zing, lime juice and zest with garlic and a bit of salt and cayenne pepper powder.
If you have a steaming basket, that's the traditional way to steam food. Bring about an inch of water to a rolling boil over high heat in a saucepan. Place the mahi mahi filet in the steaming basket and put it into the saucepan. Make sure the water doesn't touch the basket or the fish; if it does, pour a little out. Cover the pot with a tightly fitting lid. Steam the fish for about 10 minutes, until the flesh is evenly opaque through to the center and the fish breaks apart easily with pressure from a fork.
Steam your mahi mahi fillets in the oven if you don't have a steaming basket. Preheat the oven to 450 degrees Fahrenheit while preparing your recipe. Place each seasoned filet on a large sheet of aluminum foil. Pull the foil up around the fish, making a low tent over it, and scrunch the foil closed tightly. Make sure there's room above the fish for hot air and steam to circulate, but make sure there are no openings in the foil. The mahi mahi will steam in its own juices while it bakes. Cook for about 10 minutes per inch of thickness, until the flesh is uniformly opaque and flakes readily with a fork.