Bistro French Onion Soup

Rough chop onions so that slices are between ⅛ and ¼ inches thick.
Heat the butter and olive oil in a saucepan on medium heat. Once the butter has melted, add the onions and sweat them until they become translucent.
Reduce the heat to low and continue to cook the onions, stirring every 5-10 minutes to prevent them from sticking. Deglaze the pan with water or stock when the fond starts to form.
As onions continue to caramelize, stir every 5-10 minutes and deglaze the saucepan as fond forms.
Continue cooking until onions have reached a deep blonde color.

Once onions have cooked, add 4 cups of beef broth, dry vermouth, thyme, and bay leaf.
Bring the soup to a boil, and then reduce the heat.
Partially cover with a lid and simmer for 20 minutes. Season with salt to taste
Combine Gruyère and Emmentaler cheese in a medium bowl, set aside.
Place 4 oven/broiler-safe soup bowls on a cookie or baking sheet.
Fill each soup bowl with the soup, then top with 2 slices of French baguette and ½ cup of shredded cheese.
Broil until the cheese is melted and begins to brown.