WASH, trim and pound chicken to flatten to a consistent thickness.
MIX brown sugar, peanut butter, oil, soy sauce, lime juice, garlic, cayenne pepper and salt in a small bowl to make marinade.
PLACE chicken in a shallow dish (or food storage bag). Cover with marinade. Marinate 1 hour at room temperature or as long as overnight in refrigerator.
When ready to cook: HEAT grill. Combine peanut butter, coconut milk, lime juice, soy sauce, dark brown sugar, ginger, garlic and cayenne in a heavy saucepan to make peanut sauce. Cook over medium heat, stirring constantly, about 15 minutes or until thickened. Whisk in chicken stock and cream. Cook 1 minute more, whisking. Keep warm while grilling chicken.
REMOVE chicken from marinade and place on hot grill. Grill 4 to 6 minutes on each side, turning only once, until browned and no longer pink in center.
SPOON peanut sauce over hot chicken and sprinkle with cilantro.