In a large sauté pan or braiser, brown the lamb pieces in olive oil (or lard) well on all sides over a lively flame. Seasoning them generously with salt and pepper as you go.
Lower the flame and add the garlic, rosemary and sage. Sauté for just a few moments, until you can small the garlic's fragrance.
Add a good splash of white wine, turning the lamb pieces around once again to coat them well.
Now cover the pan tightly. Let the lamb braise, covered, over very gentle heat until very tender, about 30-45 minutes. Moisten the pan as needed with a few drops of wine or water.
Meanwhile, mince or mash together the garlic and anchovy into a fine paste. Moisten with a good drizzle of the vinegar.
About 10 minutes or so before the lamb is done, uncover the pot and remove the garlic and herbs you added at the beginning, then add the garlic-and-anchovy paste and mix well. Cover the pan again and finish your braise.
Serve hot.