Heat oil in a large Dutch oven coated with cooking spray over medium-high heat. Add onion; cook 20 minutes or until deep golden brown, stirring frequently.
Preheat oven to 450°.
Place bread slices in a single layer in an 11 x 7-inch baking dish. Spoon the caramelized onions over bread; sprinkle with cheeses and sage. Bring Herb Broth to a boil in a small saucepan. Pour broth around sides of dish to avoid disturbing bread layers. Bake at 450° for 22 minutes or until cheese melts. Sprinkle with parsley and pepper.