Inspired by classic French onion soup, this comforting skillet bake turns caramelized onions and creamy butter beans into a weeknight-friendly dish. Topped with a gooey blanket of Gruyère and fontina and a crisp layer of panko, it delivers all the flavors of a slow-simmered favorite in under an hour. It’s perfect for chilly evenings or anytime you want something hearty, cheesy and satisfying.