Place each chicken breast half between 2 sheets of heavy-duty plastic wrap; pound to 1/4-inch thickness using a meat mallet or rolling pin. Sprinkle chicken evenly with salt and pepper; dredge in flour.
Heat 1 1/2 teaspoons oil in a large nonstick skillet coated with cooking spray over medium-high heat. Add 2 chicken breast halves; cook 4 minutes on each side or until lightly browned and done. Place chicken on a jelly-roll pan coated with cooking spray. Repeat procedure with remaining oil and chicken. Add wine to pan, scraping pan to loosen browned bits. Bring to a boil; reduce heat, and simmer 6 minutes or until wine is reduced to 1/4 cup. Add butter, stirring until butter melts.
While sauce simmers, sprinkle sage evenly over chicken; top each piece of chicken with half a slice of prosciutto and 2 tablespoons cheese. Broil 2 minutes or until cheese melts and is lightly browned. Place chicken on serving plates; spoon sauce evenly over chicken.