In a large skillet, saute mushrooms in 2 tablespoons butter; remove and set aside. In the same skillet, melt remaining butter; stir in flour until smooth. Gradually add the milk, broth and pepper. Bring to a boil; cook and stir for 2 minutes or until thickened. Return mushrooms to the pan; stir in stuffing until blended.
Transfer to a greased 1-qt. baking dish; sprinkle with Parmesan cheese. Bake, uncovered, at 350° for 30-35 minutes or until bubbly.