Using a mortar & pestle gently crush the following ingredients: salt, black pepper, cilantro leaves, garlic, cumin seeds and red chili until the ingredients form a smooth paste. Then add the lime juice.
Rub the lamb shank with the marinade and set aside for 10 minutes.
Peel and cut the ripened mango into small cubes and place in a mixing bowl.
Chop the chili and green onion and gently mix with the mango.
Add fresh lime juice, salt and crushed pepper to the mixture and set aside.
Note: before serving mix in fresh cilantro leaves.
Cooking the barbacoa shank:
Roast in the oven at 220 degrees for 1.5 to 2.5 hours depending on size of shank. Barbacoa should be fork-tender.
Warm the tortillas on the grill or microwave. Add the barbacoa and top with mango salsa and a sprinkle of the cilantro leaves.
Serve with warm flour tortillas.