In A Skillet, Cook Chicken In Butter 3-4 Minutes On Each Side. Place Chicken In A Greased 3-Cup Baking Dish. In A Bowl, Combine Cream Cheese, Mushrooms, Onion, Salt And Pepper. Spoon Over Chicken. Unroll Dough Into One Long Rectangle; Seal Seams And Perforations. If Necessary, Trim Dough To Fit Top Of Dish And Patch Together By Overlapping Edges. Pinch Edges To Seal. Place Over Filling. Bake, Uncovered, At 350 Degrees F For 20 Minutes Or Until Heated Through.