2) Add the chicken with half the mango mixture to a resealable plastic bag, and massage to coat the chicken with the sauce. Refrigerate at least 6 hours to marinate.
3) Put the other half of the mango mixture into a small saucepan and simmer over low heat until thick, stirring often, about 15 minutes. Set some of the simmered chipotle-mango sauce aside to serve on the side. Use the rest to baste the chicken.
4) Preheat a grill or grill pan to medium-high heat and brush with oil. Remove the chicken from the marinade and put on the grill.
5) Grill the chicken turning and basting about every 5 minutes with the mango sauce until cooked through, about 20 to 25 minutes. Transfer to a serving platter and serve with the reserved mango sauce.