In a large skillet, saute mushrooms and onion in butter until tender. Stir in the sage, salt, thyme if desired, marjoram and pepper. Transfer to a large bowl. Add the bread cubes, walnuts and enough broth to reach desired moistness; toss to coat.
Spoon into a greased 2-qt. baking dish. Cover and bake at 350° for 30 minutes. Uncover; bake 10-15 minutes longer or until lightly browned. If stuffed into poultry, bake until a thermometer reads 180° for poultry and 165° for stuffing.