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.
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.
Add mushrooms to pan; saut over medium-high heat 2 minutes.
Add beef consomm, 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.
Combine reserved 1 tablespoon consomm and cornstarch in a small bowl, stirring with a whisk; add to pan. Bring to a boil; cook 1 minute or until thickened.