Start by slicing onion vertically.

Grate provolone, Swiss, and Parmesan cheese and keep it aside.

Now put a pot over medium heat and melt the butter with olive oil.

Once the butter is melted and and olive oil is heated, add sliced onions.

Sprinkle some salt and continue sautéing it until brown and caramelized, stirring occasionally for about 30 minutes.

Once the onions are tender, pour in dry sherry wine.

Afterwards add one tablespoon of flour, mix well, and cook for about a minute.

Now add in one liter of beef broth.

Now add a bunch of thyme. Let the soup simmer for 20 minutes.

Now, season it with salt and add a dash of brandy.

Preheat the oven broiler for 5 to 10 minutes. Ladle the soup in a serving bowl.

To build a crust, grill up some bread. Rub it with garlic and float on top of the soup.

Garnish grated provolone, Swiss, and Parmesan cheese on top of the bread.

Place the bowl on the broiler. Broil the soup until it turns brown and the crust is crispy for a minute or two.