French Onion Soup

recipe adapted from this
(this recipe made enough for about 4, maybe 5 large soup bowls)
4 T butter (use more if you have a lot of onions)
at least 5 big onions, thinly sliced (they will cook down)
(~48oz) chicken broth
(~14oz) beef broth
1/2 c (or more) white wine
dash of Worcestershire sauce
2 sprigs parsley
few sprigs thyme
fresh bay leaves
dash of balsamic vinegar
salt/pepper to taste
sliced bread (or croutons)
sliced Gruyere or Swiss cheese (or provel)
(optional) shredded mozzarella or asiago cheeese
Paprika to sprinkle on top

In large pot over medium heat, melt butter and then add the onions. Cook about 40min, or until onions are caramelized. Stir periodically.
Add in the chicken broth, beef broth, wine, and Worcest. sauce. Tie the parsley, thyme, and bay leaf together with string or whatever and place in the pot. Simmer 20 minutes.
Preheat oven broiler.
Discard the herbs, turn heat to low. Cover to keep warm.
Toast bread under the broiler, then remove. (I have made this with untoasted bread it still works)(Keep broiler on, going to broil the soup next).
Fill oven-safe bowls about 2/3 full with soup, top each bowl with slice of bread, and a few layers of cheese (and/or shredded cheese). Sprinkle paprika on top.
Set bowls under broiler for a couple minutes, until cheese is melty and awesome. It looks cool if you can get the cheese to melt over the edge of the bowl/

This soup freezes very well, to eat leftover just warm up the soup in microwave or stovetop, then top with a bread slice/cheese and put under the broiler for a few min.
more photos: