In a food processor or blender combine mangoes, coconut milk, salt, curry paste, curry powder, garlic powder, cumin, chili powder, lime juice, and oil. Pulse until smooth. Reserve 1/2 cup of the mixture, cover and refrigerate.
Pour remaining sauce into a large resealable bag. Add chicken, seal bag, and refrigerate for 1-8 hours (overnight works great).
Preheat grill to medium heat and lightly grease the grates. Use tongs to transfer chicken from the marinade bag to the grill. Discard bag. Cook chicken 5-10 minutes on each side until cooked through. (meanwhile move on to next step)
While chicken is cooking, transfer the reserved portion of the sauce (the portion you refrigerated by itself) to a sauce pan. Bring to a boil over medium heat and cook 3-5 minutes, then remove from heat.
Once chicken is just about cooked through, brush both sides with the sauce and allow to cook 1-2 minutes longer on each side. Serve chicken hot with any extra sauce and garnish with chopped peanuts and cilantro if desired.
Prep and cook time does not include marinating time which is 1-8 hours.