1. Pat the beef shanks dry with paper towels, then season them all over with salt and black pepper. Lightly dredge each shank in the flour and shake off the excess.

2. Heat the olive oil and butter in a large Dutch oven over medium-high heat. Sear the beef shanks for 3 to 4 minutes per side until deeply browned, then transfer them to a plate.

3. Add the onion, carrots, and celery to the same pot. Cook for 5 to 6 minutes until softened, then stir in the garlic and tomato paste and cook for 1 minute more.

4. Pour in the white wine and scrape up the browned bits from the bottom of the pot. Let it simmer for 2 minutes.

5. Stir in the beef broth, crushed tomatoes, thyme, and bay leaves. Return the beef shanks to the pot, nestling them into the liquid.

6. Cover and cook in a 325°F oven for 2 1/2 to 3 hours, until the beef is very tender and nearly falling off the bone.

7. Remove the bay leaves and thyme stems. Spoon the sauce over the beef, then finish with chopped parsley and lemon zest before serving.