Preheat oven to 350°F. Slice the top inch of the meat down, releasing it from the bone. Generously salt and pepper the lamb shanks on all sides.

Heat oil in an extra-large, heavy-bottom Dutch oven. Working in batches, brown the shanks on all sides over medium-high heat. Take your time and do this well. Set the shanks aside.

Lower heat to medium, add onions, garlic, fennel bulbs, and herbs to the same pan. Add port and stock, scraping up the browned bits and bring to a simmer. Place the shanks back in the liquid, meaty side down, bring to a boil, cover well, and place the Dutch oven, covered, in a 350°F for 1.5 hours.

In a small pot, reduce the pomegranate juice by half, simmering on medium heat, uncovered until it reduces to down to 1 cup, about 20 minutes. When shanks are tender, add 1 cup of the strained shanks cooking liquid to the remaining pomegranate juice. Plate the shanks and drizzle a little pomegranate sauce over the top, garnishing with fresh pomegranate seeds.