From Epicurious. Other reviewers suggested sauteeing onions as well and adding beef/chicken stock instead of water to add further flavour. I am going to do this with deboned leg of lamb and cook on low heat for 2-3hours.
Pat the pieces of lamb dry with paper towels and sprinkle generously with salt and pepper.
In a heavy saucepan or casserole, gently sauté the garlic and rosemary in the oil over medium-low heat until the garlic is soft but not brown, about 10 minutes. Add the seasoned lamb, raise the heat to medium, and turn the lamb pieces, stirring constantly, until they have browned thoroughly on all sides. Add the wine, let come to a simmer, and cook until reduced by half.
Stir in the olives and the dissolved tomato paste, mixing everything together, then cover the pan and continue cooking on very low heat for about 1 hour, or until the sauce is very thick and the lamb is cooked through. Check the sauce periodically and add more wine or water if it seems necessary.
When the lamb is done, serve it immediately, accompanied by polenta, if you wish.