Flatten turkey breasts to 1/4 inch thickness. Season flour with salt and pepper . Place flour in a resealable plastic bag;add turkey. Seal and shake to coat.
In a skillet,brown turkey in 2 T butter on both sides. Transfer to a greased 11x7 inch baking dish. In the same skillet saute mushrooms,garlic and onions in the remaining butter till onion is tender. Add the broth,salt and pepper to taste. Bring to a boil;cook 5 minutes or until liquid is reduced to half. spoon over turkey.
Bake,covered at 375 deg. for 15 minutes. Sprinkle with green onions. Bake 5 minutes longer or until juices run clear.