1. Preheat oven to 350°F (175°C).
2. Season veal shanks with salt and pepper, then dust with flour.
3. Heat olive oil and butter in a Dutch oven over medium heat. Brown the veal shanks on all sides. Remove and set aside.
4. In the same pot, add carrots, celery, and onion. Cook until softened, about 5 minutes. Add garlic and cook for another minute.
5. Pour in white wine, scraping up any browned bits from the bottom of the pot. Let it reduce by half.
6. Add chicken broth, diced tomatoes, thyme, and rosemary. Return the veal shanks to the pot. Bring to a simmer.
7. Cover the pot and transfer to the preheated oven. Cook for about 2 hours, or until the meat is tender and falling off the bone.
8. Serve hot, garnished with gremolata if desired.