In a large pot, combine the onions, seasoning, thyme, bay leaf, and olive oil. Cook on low for 30 to 45 minutes until the onions are soft and transparent.
Remove the thyme and bay leaf, then add the flour and stir until well combined.
Deglaze with white wine and scrape the bottom of the pot. Add the beef broth, and Worcestershire sauce. Stir and simmer for an additional 30 minutes.
Ladle the soup into oven-safe bowls. Top each with a piece of Texas toast and load it with gruyere.
Place under the broiler until the cheese is melted and bubbly.
