Trim the fat off the lamb leg and make a dozen deep cuts into the meat with a sharp knife.

Combine the butter, garlic, salt, pepper, cumin, saffron, turmeric and olive oil. Spread mixture over the lamb leg and massage into the knife incisions.

Line the bottom of the slow cooker with the thinly sliced onion.

Place the lamb shanks onto the onion.

Sprinkle the rosemary over the lamb shanks.

Prepare the 1 cup of gravy and pour over the lamb shanks.

Place lid on the slow cooker and cook on low for 6-8 hours stirring occasionally.

Remove from slow cooker and allow to rest for 10 minutes before serving.