1. Sprinkle chicken evenly with salt and 1/4 teaspoon pepper; coat with cooking spray. Heat a large nonstick skillet over medium-high heat. Add chicken to pan; cook 5 to 6 minutes on each side or until browned.

2. While chicken cooks, cut shallots vertically into thin slices to measure 1 cup. Remove chicken from pan. Coat pan with cooking spray. Add mushrooms and shallots to pan; coat vegetables with cooking spray. Cook 1 minute, stirring constantly. Stir in sherry and marjoram. Return chicken to pan; cover and cook 3 min or until mushrooms are tender and chicken is done. Transfer chicken to a platter. Spoon mushroom mixture over chicken; sprinkle with freshly ground pepper, if desired.