Preheat oven to 325 degrees F.

Combine the spices for the lamb including cumin, paprika, salt, coriander, and black pepper. Sprinkle the spice mixture over the lamb shoulder, making sure to cover all the sides. Let sit for 20 minutes.

Heat 2 tablespoon oil in a Dutch oven over medium-low heat. Add the lamb and sear on all sides until lightly browned. Remove the lamb from the pot and set it aside.

In the same pot, heat another 2 tablespoon oil. Add the sliced onions and saute until caramelized, about 20 minutes. If the pot becomes too dry, add a couple of tablespoons of water. Add the chipotle with the adobo juices, smooth ale, 2 tablespoon pomegranate molasses, rosemary, garlic, and chicken stock, and bring to a boil. Add the lamb shoulder to the pot, cover, and continue to braise in the oven for 3 hours or until the lamb is tender.

Remove the lamb from the pot and skim the fat from the braising liquid. Increase the heat to high and boil the liquid until it's reduced by half. Add 2 tablespoon brown sugar, 1 tablespoon pomegranate molasses, and the cornstarch and water slurry. Continue to simmer until the sauce has thickened. Season with salt and pepper.

Slice the lamb shoulder and pour the sauce on top. Sprinkle fresh pomegranate arils and serve.