Step 1Saute the pancetta in 1 tablespoon olive oil over medium low heat in a braising pan (or a large, heavy-bottomed ovenproof pan) until the pancetta is crispy and the fat is rendered, about 15 minutes. Remove the crisp pancetta from the pan and set aside.
Step 2Heat 2 tablespoons olive oil in the same pan and add the cipollini. Cook until browned on all sides, about 5 minutes. Remove from the pan.
Step 3Add the diced onion, carrots and celery to the pan and cook until tender, about 10 minutes. Add the garlic and mushrooms and cook until tender, about 5 minutes. Transfer the vegetables to a bowl and set aside.
Step 4Pat the veal shanks dry with a paper towel. Sprinkle both sides of the meat with the fennel seeds, fleur de sel and cracked pepper and rub the spices in. Roll the meat in the flour to coat.
Step 5Heat the remaining 2 tablespoons oil and 1 tablespoon butter in the same pot. Add the veal and cook until browned on all sides, about 10 minutes.
Step 6When the veal is well browned, return the reserved pancetta, cooked vegetables and cipollini to the pot. Pour in the wine. Blend the tomato paste with a little of the stock and pour in along with the remaining stock. Add the thyme sprig and bay leaf. Bring the mixture to a simmer.
Step 7Remove the pot from the heat, cover and put it on the middle rack of a 325-degree oven. Cook until the veal is fork tender, about 2 hours.
Step 8To serve, carefully transfer the meat from the pot to a serving platter and keep warm. Skim off any excess fat from the top of the sauce. Place the pot back on a burner and, over medium heat, bring the sauce and vegetables to a boil. Reduce the heat and simmer until the sauce is slightly thickened, about 5 minutes. Spoon the sauce over the meat and arrange the vegetables alongside. Pour any additional sauce into a gravy boat. Serve with lemon risotto.