1. Place bread in a food processor; pulse 10 times or until course crumbs measure 1/3 cup. Combine crumbs, beef, egg, and onion in a bowl. Shape into 6 (1/2-inch-thick) patties.
2. Heat a large nonstick skillet over medium-high heat; coat pan with cooking spray. Add patties; cook 5 minutes on each side or until browned. Transfer patties to a platter, and keep warm.
3. Add mushrooms to pan; sauté over medium-high heat 2 minutes. Add beef consommé, reserving 1 tablespoon. Add mushroom soup and pepper; stir well to combine. Add patties. Bring mixture to a boil; reduce heat, cover, and simmer 20 minutes.
4. Combine reserved 1 tablespoon consommé and cornstarch in a small bowl, stirring with a whisk; add to pan. Bring to a boil; cook 1 minute or until thickened.