Heat oven to 375° F. Prepare baking dish with nonstick cooking spray.

Cut each chicken breast in half. Place flour in resealable bag. Place chicken in resealable bag with flour; toss to coat.

In large skillet, melt butter. Add chicken to skillet; brown all sides. Transfer chicken from skillet to 11-by-7-inch baking dish.

In skillet, saute sliced mushrooms in remaining butter until softened. Add chicken broth, salt and pepper. Bring to boil then cook 5 minutes. Spoon over chicken.

Bake 15 minutes. Sprinkle with cheeses and green onions. Bake 5 minutes, or until cheese is melted.