In small saucepan over medium heat, stir the butter with the honey and sugar until the butter melts. Remove from heat. Add the mustard, soy sauce, oil, and garlic; mix well and let cool.
Remove the bones from the fish (or have the seafood shop do it for you). Rinse and pat the fish dry with paper towels. Set the fish skin-side-down in a foil-rimmed pan. Spoon the sauce over and marinate for one hour.
Bake in a covered barbecue (with vents open) for 8 to 12 minutes. This may also be baked in the oven at 425℉. for 10 to 15 minutes (depending on the thickness of your fish), or until the fish flakes apart easily with a fork. Serve with lime wedges.
Notes
If you're preparing this recipe as GLUTEN FREE, just make sure that you are using GF varieties of both honey and soy sauce.