Preheat oven to 300° F.

Season the lamb shanks with salt and pepper.

Heat a large saucepan or Dutch oven to medium heat. Lightly coat the pan with olive oil. Season lamb shanks with salt and pepper. Sear shanks in pan until golden brown and caramelized (about 10 minutes). Remove the lamb and set aside.

Add the onion, carrot, fennel, and garlic to the pan and saute until golden, about 10 minutes. Stir in tomato paste and lightly brown as it coats the veggies(about 3 minutes). Add the white wine, chicken broth, and rosemary and place shanks back in the pan.

Cover the pan and braise the lamb until the meat is very soft (about 2 hours).

Uncover pot, simmer until meat is very tender, about 30 minutes more.

Transfer shanks to platter. Boil sauce in pot until thickened about 15 minutes. Season with salt and pepper and spoon over shanks.