In a cast iron skillet, combine onions, with butter and olive oil.
Season with salt and pepper to taste.
Place over indirect heat in a preheated 350-degree charcoal grill. Place your favourite wood underneath the lit charcoal for extra smoke flavour (we love using a fruit wood like apple or peach!)
Allow the onions to caramelize, stirring occasionally, until reduced and nicely browned – about an hour.
Deglaze the pan with the bourbon.
Add the fresh rosemary, and beef broth, and bring to a low simmer.
Ladle into French onion soup bowls, top with baguette and cheese, and return to the grill. Once the cheese is melted, the soup is ready!
Top with freshly cracked black pepper.