Melt 1 stick of butter in a large pot.
Thinly slice 3-4 large onions and place in the pot.
Cook the onions on medium heat until they are golden brown stirring occasionally. This could take up to 45 minutes.
Once onions are fully caramelized, deglaze pot with red wine. (optional). I just put a splash in and stir well until nothing is sticking to the bottom of the pot.
Pour in beef broth and chicken broth.
Add in beef base, garlic salt and thyme.
Add in flour and stir allowing soup to thicken a bit.
Turn on the broiler.
Ladle soup into sourdough bread bowls or oven safe bowls and place on a baking sheet.
Cover with cheese of your choice, provolone is our favorite.
Allow to broil in oven for 3-4 minutes until cheese is melted and bubbly.
Enjoy!