How to Make It
In a small bowl, whisk together the brown sugar, ketchup, soy sauce, sesame oil, vegetable oil, ginger and half of the minced garlic.
In a medium frying pan, heat the extra-virgin olive oil over medium high heat. Add the onion and cook 5 minutes, until it starts to brown. Add the tilapia to the pan, and pour the sauce over top. Cook for 6 minutes, or until the fish flakes easily. When the tilapia is cooked through, break it into small pieces with a wooden spoon.
Divide the tilapia between the butter lettuce leaves and wrap the lettuce around the fish taco-style.