1 can (15 ounces) black beans, rinsed and drained
1/4 cup plain bread crumbs
2 tablespoons ketchup
2 tablespoons minced onion
1 teaspoon Worcestershire sauce
1/2 teaspoon salt
1/4 teaspoon black pepper
1/2 teaspoon garlic powder
3 tablespoons olive or canola oil, divided
1 cup thinly sliced red onion (about 1 medium onion)
2 portobello mushrooms, stems removed and caps sliced about 1/2-inch thick
1 teaspoon minced garlic
(about 2 medium cloves)
1 to 2 tablespoons all-purpose flour
4 slices sharp Cheddar cheese (about 1-ounce each)
4 toasted hamburger buns
prepared mustard (optional)
Mash beans in a medium bowl with potato masher or fork. Add bread crumbs, egg, ketchup, minced onion, Worcestershire sauce, salt, pepper, and garlic powder and mix well. Cover and chill.
Heat 1 1/2 tablespoons oil in skillet over medium heat and add red onion and sliced portobellos and sauté about 5 to 7 minutes, until tender. Add minced garlic and cook 1 minute more. Remove onions and mushrooms from skillet and set aside.
In same skillet, heat remaining 1 1/2 teaspoons oil over medium heat. Dust hands with flour and shape bean mixture into 4 patties and add to skillet. Cook patties about 4 to 5 minutes on each side until lightly browned.
Top each patty with one-fourth of the mushrooms and onions and then with 1 slice of cheese. Allow cheese to melt.
Serve on toasted buns with ketchup and mustard, if desired.