If it's too cold to go outside, use a grill skillet to cook the chicken. The Mango Salsa is also delicious served over broiled salmon. Substitute 1 (26-ounce) jar of sliced, refrigerated mangoes if fresh are not available.
Combine first 5 ingredients in a shallow dish or heavy-duty zip-top plastic bag; add chicken. Cover or seal, and chill 1 hour, turning once.
Remove chicken from marinade, discarding marinade.
Grill, covered with lid, over medium high heat (350° to 400°) 6 minutes on each side or until done. Drizzle with Mustard Sauce; sprinkle with chopped nuts. Serve with Mango Salsa.