Step 1

Preheat the oven to 375 degrees F.

Step 2

In a Dutch oven large enough to hold the shanks in a single layer, heat the oil over medium heat. Arrange the meat on a flat surface and sprinkle generously on all sides with salt and pepper. When the oil begins to smoke lightly, add the shanks in a single layer to the pan, working in batches if necessary so as to not crowd the pot. Brown them on the first side for 5 to 8 minutes. Use a pair of metal tongs to turn on the second side and brown for just as long. Don’t rush the browning. Allow the shanks all the time they need. This browning is the most important part of building deep flavor. Move the meat to a plate and set aside.

Step 3

Add the onions, carrots, garlic and bay leaves to the Dutch oven and cook until the vegetables take on some color. Add the wine and tomatoes; it’s not necessary to crush the tomatoes, as they’ll melt into the liquid. Return the shanks to the pot and add the beef stock. Bring the liquid to a simmer over medium heat and skim any impurities. Cover and place the Dutch oven in the center of the oven. Cook until the shanks are completely tender, 2 to 2 1/2 hours. (If the meat is not completely tender, don’t be afraid to cook it longer. It’s much easier to undercook than overcook this dish.)

Step 4

Remove the pot from the oven, uncover, and let sit for 15 minutes to rest. Use a large slotted spoon or tongs to remove the shanks to a large shallow bowl or serving platter. Sprinkle the meat with salt. Remove half of the braising liquid and save for another use or dispose. Reduce the remaining liquid by half over medium heat, 15 to 30 minutes. Remove the bay leaves. Stir in the orange zest (be sure they are LIGHT grates; we barely want to detect it) and the vinegar. Taste for seasoning. Pour the sauce over the meat and dot the shanks with more vinegar.

Step 5

Serve the osso buco with the Sautéed Spinach.

Step 6

Heat half the oil in a 12-inch skillet over medium heat. When the oil begins to smoke lightly, add half the spinach with a pinch of salt and remove the skillet from the heat. Cook, stirring with a wooden spoon, until the spinach loses half its volume. Repeat with the remaining oil and spinach. Serve as a side dish.