Put the ingredients for the marinade in a food processor or blender and blend until smooth. Coat the chicken thighs in the marinade and refrigerate for 1-4 hours.
After marinating, Heat an indoor or outdoor grill to about 400 degrees F (medium high heat). Place the chicken onto the grill and grill 5 to 6 minutes per side, until the chicken is cooked. Remove the chicken from the grill and let rest for 10 minutes.
Meanwhile - clean the butter lettuce and separate it into cups.
Combine the mango, red onion, bell pepper, avocado, mint, cilantro and lime juice in a bowl and toss to combine. Season with salt and pepper.
Assemble the lettuce cups with a piece of chicken, a few tablespoons of the topping and serve with extra limes if needed.