
In a medium bowl, combine egg, cracker crumbs, onion, salt, pepper and sage. Add beef and mix well. Shape into 2 patties.
In a medium skillet, cook patties until browned, 4-5 minutes per side; drain. Remove to a platter and keep warm.
In the same skillet, saute mushrooms in butter for 2 minutes. Stir in flour; blend well. Add water and bouillon; cook and stir until smooth and thickened. Stir in browning sauce if desired. Return patties to gravy and cook, uncovered, over low heat until heated through, about 10 minutes, turning occasionally. Serve with mashed potatoes. If desired, sprinkle with parsley.