Lamb
Preheat the oven to 250°F.

With a small, sharp knife, mince together the salt and garlic. Then, poke holes all over the lamb and insert some of the salt-garlic mixture into each hole, smearing any of the remaining mixture over the surface of the meat; and sprinkle with additional salt and pepper.

Place the lamb in a heavy roasting pan with lid . Cover and cook in the oven for 4 hours. Then, remove the lid and cook another 2 hours, until a sharp-bladed knife can be easily inserted into the meat. If the lamb’s skin is not yet nicely browned, raise the heat to 400°F and cook another 10 minutes or so.

Mint Sauce and Serving
For the mint sauce, in a saucepan over high heat, combine the sherry vinegar, sugar, water, and pinch of salt. Bring to a boil for about 30 seconds. Remove from the heat and cool for a few minutes at room temperature. Then pour the mixture into a blender, add the mint, and blend until smooth, following the manufacturer’s instructions for working with hot liquids. Transfer to a sauceboat or bowl and serve at room temperature.

Carefully transfer the lamb to a wooden cutting board and, steadying the roast with a carving fork, carve into thin slices with a sharp knife. Arrange the slices on a platter, garnish with rosemary, and pass the sauce alongside.