Combine beef, crumbs, milk, Worcestershire sauce, 1/2 teaspoon salt, pepper and garlic powder; mix well. Shape into 3 or 4 oval patties; cook on both sides until no longer pink. Cook the mushrooms and basil in 2 Tablespoon butter over medium-high heat until tender. Increase heat to high; cook and stir until most of the liquid evaporates. Melt the remaining butter; stir in flour. Gradually blend in cream. Add 1/2 cup water, hot pepper sauce and remaining salt; cook and stir on low until thickened and bubbly. Cook and stir for 2 minutes more. Add enough remaining water to make a medium-thin sauce. Add mushrooms; heat through. Serve over beef patties; top with cheese and onions.