There are similar recipes which call for simmering the garlic in water. While acceptable, the sauce is much improved if the garlic is roasted. This method also yields the by-product of garlic-flavored oil for other uses.
While the USDA recommends cooking whole muscle meats to a temperature of 145° for safety, many people prefer it rarer, at 125° to 130°. If that’s your preference, check for doneness about ¾ of the way through the roasting time. One of the nice things about a leg of lamb is that it’s still delicious even when cooked much longer, though, so it won’t be ruined if you don’t catch it in time. The choice is yours.
This is a generous recipe, good for a crowd. You can certainly make a smaller roast.
- 6-8 lb. leg of lamb, bone-in
- 10-12 large garlic cloves, peeled
- Olive oil to coat garlic cloves
- 2 cups meat stock, preferably lamb
- 4 TB tomato purée
- 2 TB cornstarch
- Cold water
- Preheat the oven to 400°F
- Place the leg of lamb in a roasting pan, season with salt and pepper, and roast for 15 minutes per pound of meat
- If you prefer your lamb on the rarer side, check the temperature about ¾ of the way through the estimated cooking time
- Put the garlic cloves, well coated with olive oil, in a small covered baking dish or a twist of heavy duty aluminum foil
- Put in the oven with the lamb to roast for the last 45 minutes of cooking
- When the lamb is done, remove it from the oven and tent loosely with foil
- Purée the garlic, and transfer to a medium saucepan
- Add the stock, the roasting juices from the lamb, and the tomato purée
- Simmer for a few minutes to reduce a little and allow the flavors to blend
- Make a slurry of the cornstarch with enough cold water to make it pourable
- Whisk into the simmering sauce and continue whisking until the sauce thickens
- Taste and season with salt and pepper as needed
- Carve the lamb
- Add any additional juices from the cutting board to the sauce, and serve with the lamb