1Heat oven to 400°F. In 13x9-inch pan, melt 1/4 cup butter in oven. Toss bread cubes in butter until evenly coated. Sprinkle with cheese. Bake uncovered 10 to 15 minutes, stirring occasionally, until golden brown and crisp.
2Reduce oven temperature to 325°F. In 4-quart ovenproof Dutch oven, melt 1/4 cup butter over medium heat. Stir in brown sugar and Worcestershire sauce. Toss onions in butter mixture.
3Bake uncovered about 2 hours 30 minutes, stirring every hour, until onions are deep golden brown. Remove from oven; stir in broth and water. Heat to boiling on top of stove. Serve with croutons.