INGREDIENTS
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1 pound onions, cut into 1/2-inch-thick rings
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2 tablespoons olive oil
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2 tablespoons balsamic vinegar
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1 tablespoon soy sauce
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1 1/2 teaspoons packed brown sugar
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1 1/2 pounds beef flank steak
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2 tablespoons Worcestershire sauce
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1 tablespoon olive oil
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Ground black pepper
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1/2 cup shredded Muenster cheese (2 ounces)
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1/2 cup shredded Fontina cheese (2 ounces)
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1/2 cup shredded American cheese (2 ounces)
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6 soft hoagie rolls or other soft sandwich rolls