In a large Dutch oven, heat 2 tablespoons of olive oil over medium-high heat. Season beef short ribs with salt and pepper, then brown them for about 8 minutes.

Add 3-4 thinly sliced yellow onions to the pot, stirring to coat in the drippings. Cook for about 10-12 minutes until onions are soft and caramelized.

Stir in 4 minced garlic cloves and cook for 1-2 minutes until fragrant. Add 2 teaspoons of fresh thyme and 1 bay leaf, stirring to combine.

Pour in 1 cup of dry white wine, scraping the pot's bottom to deglaze. Allow the wine to simmer for 2-3 minutes.

Return the short ribs to the pot along with 6 cups of beef broth. Bring to a gentle simmer, then reduce heat to low and cover. Cook for 2-3 hours.

Remove the short ribs from the pot, shred the meat, and return it to the pot. Stir well to combine.

Preheat the oven to 400°F (200°C). Slice a baguette and toast for about 5 minutes until golden.

Ladle the soup into oven-safe bowls. Top each with a slice of toasted baguette and sprinkle with Gruyère and Parmesan cheese. Broil for 2-3 minutes.

Let cool slightly before serving. Enjoy hot with melted cheese and toasted bread.