Preheat oven to 350°F. Place bread slices on baking sheet; brush with melted butter. Bake 10 to 15 minutes or until golden brown. Set aside.
Heat oil in large nonstick skillet over medium-high heat. Add mushrooms; cook and stir 5 minutes. Add sherry, garlic, Italian seasoning and salt; cook and stir 3 minutes longer or until liquid is evaporated and mushrooms are golden.
Spoon mixture evenly over bread. Layer with French Fried Onions and cheeses, beginning and ending with onions. Bake for 5 to 8 minutes or until cheese is melted and onions are golden. Serve warm.
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