Pat dry the fish inside and out. Season inside and out with salt and pepper. Mix the key limes, onions, ginger, and olive oil together. Stuff the fish with the mixture. Rub the outside with a little of the olive oil. On a prepared (cleaned and oiled), medium hot grill, place the fish and grill both sides. Watch for flare-ups. Have a squirt bottle of water handy to prevent burning. Cook the fish for about 10 to 12 minutes a side or until the fish is flaky. Let rest for 5 minutes before serving.
On a large oval, zig-zag the mango brown butter. Place the plantains on the plate and top with fish. Drizzle some more brown butter on the fish.
Beverage: Fresh Key Lime Margaritas (3 parts 100 percent agave tequila like Herradura or Patron, 2 parts lime juice and 1 part Cointreau) or Virgin Margaritas
Mango Brown Butter Vinaigrette: Heat the butter in a small skillet over low heat until it browns, about 10 minutes. Watch carefully as the butter can burn quickly, after browning. It will smell like buttered popcorn.
In a blender combine the mango, juices, Dijon and shallots. Blend until smooth. Add the hot butter while blender is on. Season and check for flavor. Keep at room temperature. For storage overnight, keep in the refrigerator and bring back to room temperature for service.
Gingered Smashed Plantains: In a heavy skillet, coat well with oil and bring to medium-high heat. Season the plantains and saute until brown. Flip to brown other side. Drain on paper towels. Lay each slice topped with a little minced ginger on a 5 by 10 triple folded piece of aluminum foil. Fold foil over and smash with saute pan, pot or mallet. to form a small pancake. Reheat pan to medium heat and coat with oil. Saute the 'pancakes' until cooked through. (Can be easily pierced with a fork.) Right before serving drizzle with honey and toss with the scallions.;