Start by heating 2 tablespoons of olive oil in a large Dutch oven over medium-high heat. Once shimmering, add the beef short ribs, searing them on all sides for about 8–10 minutes until they achieve a rich brown color. Remove the ribs and set them aside.

In the same pot, reduce heat to medium and add 3 tablespoons of butter. Add 4 sliced yellow onions and cook them for 30–40 minutes, stirring frequently, until deep golden brown.

Stir in 3 minced garlic cloves and sauté for 1 minute until fragrant. Pour in 1 cup of dry red wine, scraping the bottom of the pot, and let it simmer for 3–5 minutes.

Return the seared short ribs, 4 cups of low-sodium beef broth, 2 diced carrots, 2 diced celery stalks, 2 sprigs of fresh thyme, and 1 bay leaf to the pot. Bring to a boil, then reduce to low and cover. Simmer for 2.5 to 3 hours.

Remove the short ribs and let them cool slightly. Shred the meat off the bones using two forks. Strain the broth through a fine mesh sieve, returning the solids if desired.

Preheat your broiler. Slice a fresh baguette and place on a baking sheet. Top each slice with grated Gruyère cheese. Broil for about 2–4 minutes until cheese is bubbly and golden.

Ladle the soup into bowls and top with cheesy Gruyère toasts before serving.