Melt 4 tbsp butter in a heavy pot over medium heat
Add 6 thinly sliced onions, 3 cloves chopped garlic, 2 bay leaves, 2 tbsp fresh thyme, salt and pepper
Stir frequently for 30 minutes until deep golden brown
Deglaze with 1 cup white wine, scraping up all the browned bits
Add 1 quart beef stock and 2 tbsp Worcestershire sauce
Simmer for 15 minutes
Slice baguette into 1-inch rounds and toast at 250°F for 15 minutes
Pile shredded Gruyere (½ lb total) on top of croutons
Broil for 2-3 minutes until melty and bubbly
