Over medium heat, melt the butter in a large stock pot.
Add onions and cook for 20-30 minutes until caramelized.
Add garlic, bay leaves, thyme, and red wine to the mixture.
Bring to a boil, then reduce and simmer for 5-10 minutes until the liquid evaporates.
Sprinkle the flour over the onion and wine mixture. Stir to coat the onions.
Reduce heat to medium to avoid burning.
Cook for approximately 10-12 minutes.
Add the water and beef base. Stir to combine.
Bring soup to a simmer for 15-20 minutes.
Add salt and pepper to taste.
Ready to Serve?
Slice the baguette into ¼ to ½ inch pieces.
Place baguette slices on a baking sheet and toast in the oven for 3-4 minutes.
Ladle the soup into soup ramekins or oven-safe soup bowls. Place 2 to 3 slices of the baguette on top. Generously sprinkle the shredded Gruyere cheese on top.
Place bowls on a baking sheet and place them in the oven.
Bake until the cheese is melted.
Remove and serve. Be careful - the soup will be hot!
Notes
Culinarian Tips, Tricks, and Suggestions: There are many options for oven-safe bowls for this soup. We have found that large ramekins have been a great option.