Slowly cook the chopped onions in butter until caramelized. Mix onions with white wine and beef broth. Spread the bottom of a pan with the onion spread and top with thick cut slices of toasted baguette. Bake in the oven at 350⁰F. After 15 minutes, take out the baked sandwich from the oven and top with your favorite cheese. Put the pan back in the oven and bake for a few more minutes. Sprinkle fresh herbs over the baked sandwich before serving.