Thinly slice one-and-a-half onions;finely chop remaining half onion. In a large bowl,toss bread crumbs with Chopped onion and seasonings. Add beef; mix lightly but thoroughly. Shape into four 1/2-in-thick oval patties.

Place a large nonstick skillet coated with cooking spray over medium heat. Add patties ;cook 5to6 minutes on each side or until a thermometer reads 160. Remove from pan. Discard drippings from pan.

In a small bowl,mix cornstarch,bouillon and water until smooth. In same skillet. Heat butter over medium-high heat. Add mushrooms and sliced onions cook and stir 5-7 minutes or until onions are tender.

Stir in cornstarch mixture. Bring to a boil; cook and stir 1-2 minutes or until thickened. Return the Salisbury steaks to pan, turning to coat with sauce; heat through.