Melt butter, add stuffing (and seasoning) and mix well. Spread 3/4 of stuffing mixture in bottom of greased 11 x 7 inch casserole. Lay pieces of chicken on top of stuffing. Add drained mushrooms. Mix well sour cream, cream of chicken soup and 1 cup chicken broth. Spoon over chicken and dressing. Sprinkle remaining 1/2 cup chicken stock and stuffing over top. Bake 45 minutes at 350 degrees.
Or mix all ingredients together in casserole dish and bake. (This is what I do.)