Arrange chicken in a 13- x 9- x 2-inch baking dish coated with cooking spray. Top chicken with ham and cheese.
Coat a nonstick skillet with cooking spray; place over medium-high heat until hot. Add mushrooms; saute until tender. Combine mushrooms, soup, and sherry. Spoon mixture over chicken. Top with stuffing mix; coat well with cooking spray. Bake at 350° for 45 minutes.