Preheat grill to medium high heat. Lightly oil grill grate.
Saute' onions and mushrooms in olive oil. Add cooked bacon and cheese. Set aside.
Place ground sirloin, Worcestershire sauce, garlic powder, salt and pepper into a large bowl. Mix and shape into 10 thin patties.
Place a single thin patty onto a plate, and add 1 heaping tablespoon of the sauteed mixture into the center of the patty. Now add another thin patty on top of filling and center with the other patty. Press edges of the patty closed, to form one burger patty.
Editor's Note: If you want to make your stuffed burgers more uniform there are Stuffed Burger Presses available like the one pictured above that will accomplish that task. Now your next question is do these stuffed burger presses actually work. Well take a look at the video below from ABC NewsWatch 12 in Medford, Oregon. They put a popular stuffed burger press called the STUFZ Burger Maker to the test.
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