World'S Greatest Mushroom-Onion Burgers

• 4 tablespoons butter or 4 tablespoons margarine
• 1 large onion, chopped
• 6 ounces mushrooms, chopped
• 1 1/2 lbs ground sirloin
• 1 1/2 teaspoons salt
• 1 teaspoon fresh ground black pepper
• 1 tablespoon A.1. Original Sauce
• flour (for dredging)
• 2 tablespoons olive oil (preferably extra-virgin)
• 5 large kaiser rolls, lightly toasted
• Accompaniments
• cheese, of your choice (optional)
• sour cream (optional)

1. In a large, heavy skillet, melt butter or margarine.
2. Cook onions over medium-low heat until golden brown.
3. Add the mushrooms and continue cooking until mushrooms are tender.
4. Let sit until cool enough to handle.
5. In a large bowl, mix the sirloin, salt, pepper, steak sauce, and onion-mushroom mixture.
6. Form into 5 burgers.
7. In same skillet, heat olive oil over medium heat.
8. Dredge burgers in flour and cook until desired doneness, turning once.
9. Add cheese (if desired) and melt atop burger.
10. Top with a dollop of sour cream.

butter, onion, mushrooms, ground sirloin, salt, fresh ground black pepper, original sauce, flour, olive oil, kaiser rolls, accompaniments, cheese, sour cream

Taken from www.food.com/recipe/worlds-greatest-mushroom-onion-burgers-138617 (may not work)