Heat the grill to medium-high heat, about 350 degrees F.
To make the salsa: Grill the mango, onion, avocado, jalapeno, and limes until char marks appear, about 5 minutes. Dice the grilled mango, onion, avocado and jalapeno and transfer to a medium bowl. Squeeze the lime into the mixture, adding mint, olive oil, salt, and pepper to taste. Refrigerate until ready to serve.
To make the fish: Tear off 4 large sheets (about 16-inches long) of heavy-duty foil. Place one piece of fish in the center of each. Top each fillet with 1 tablespoon jalapeno lime butter and two lime slices. Fold up the ends of the foil and seal into packets.
Grill the packets over medium heat until cooked through, about 5 minutes on each side.
To serve: Remove the fish from packets and garnish with grilled mango avocado salsa.
*Cook's Note: This is a compound butter made from butter mixed with grilled jalapenos and lime juice.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.