For caramelized onions; combine the onions and brown sugar and cook slowly stirring often, until the onions begin to turn brown (about 15-20 minutes). Stir in the wine and vinegar and heat at medium to bring to boil. Reduce heat and cook, stir often until most liquid is evaporated (30 minutes). Set aside.
Preheat over at 350 degree F while onions are cooking. Combine mustard, lemon juice, pepper, Worcestershire sauce and garlic. Place chicken in dish previously sprayed with non stick oil and cover with mustard mixture.
Bake uncovered for 30 minutes or until chicken is white through. Serve with caramelized onions over top.
Serves 4 people.