In a small bowl, mix together the pomegranate molasses, kosher salt, black pepper, nutmeg, and cinnamon.
Rub the marinade all over the lamb shanks, ensuring they are well coated. Let them marinate for at least 1 hour, or preferably overnight in the refrigerator.
Heat olive oil in a large Dutch oven over medium-high heat. Sear the marinated lamb shanks on all sides until nicely browned. Remove and set aside.
Add the sliced red onions and smashed garlic to the pot. Sauté for about 5-7 minutes until the onions are translucent.
Pour in the stock and scrape the bottom of the pot to release any flavorful bits stuck to the bottom.
Stir in the pomegranate juice, sugar, and lemon juice. Bring to a simmer.
Return the lamb shanks to the pot, cover, and reduce heat to low. Allow to braise for 2.5 to 3 hours, until the meat is tender.
Once cooked, remove the lamb shanks and let the sauce reduce for about 10-15 minutes until it thickens.
Arrange lamb shanks on a serving platter, drizzle with sauce, and garnish with pomegranate arils, parsley, and chili peppers.