1. In a large pot, heat olive oil over medium heat.
2. Season the beef short ribs with salt and pepper, then sear them in the pot until browned on all sides, about 4-5 minutes each side. Remove the ribs and set aside.
3. In the same pot, add the sliced onions. Cook, stirring occasionally, until they caramelize and turn golden brown, about 15-20 minutes.
4. Add the minced garlic and cook for another 1-2 minutes until fragrant.
5. Return the beef short ribs to the pot and pour in the beef broth. Add balsamic vinegar, thyme, bay leaf, and more salt and pepper if desired.
6. Bring the soup to a boil, then reduce the heat to low. Cover and let it simmer for about 1.5 to 2 hours, until the meat is tender.
7. Preheat your oven broiler. While the soup is simmering, place the French bread slices on a baking sheet and toast them lightly in the oven.
8. Once the ribs are tender, remove them from the pot, shred the meat, and discard the bones. Return the meat back to the soup and stir.