In a large stockpot, saute onions in butter, with bay leaves, until golden brown. Stir frequently to prevent burning, but you do want a rich, golden brown color.
Once golden brown color is reached, deglaze with wine and simmer for 15 minutes.
Next, add in beef broth, salt and pepper...adjusting spices to taste.
Bring mixture to a boil, then turn to a low simmer for 30 minutes.
Serve soup immediately with croutons and cheeses, or store in refrigerator for 3-4 days. Freeze for 2-3 months. The flavor actually deepens after being frozen.