Salisbury Steak Surprise With Ground Mushroom Gravy

In a large bowl, combine sirloin, onion, tomato paste, salt, and pepper.

Form mixture into 4 oval patties.

Stuff a piece of blue cheese into center of each patty, sealing well.

Over medium heat, melt the olive oil and butter in a large, heavy skillet.

Dredge patties in flour, and brown on both sides.

Pour beef broth over patties and cover.

Cook for 20 to 25 minutes.

Transfer patties from skillet to serving platter and keep warm.

Put mushrooms in food processor fitted with a steel blade.

Process until finely ground.

Add mushrooms to skillet and simmer for 10 minutes, or until mixture is thickened.

Serve gravy over cooked patties.