Preparation

At least 1 day ahead marinate the lamb:

• Set the lamb flat on a large cutting board. Trim any excess fat and then make deep horizontal slices into the thicker parts and open like a book to make an even thickness all around. Lay a piece of plastic wrap on top of the lamb and using a meat mallet or the bottom of a heavy skillet, pound to flatten slightly and make the thickness more uniform. Cut the meat into 2 or 3 more-manageable pieces. Sprinkle all over with 1 Tbs. of the salt and 1 tsp. of the pepper.
• In a small bowl, mix the mustard, garlic, thyme, rosemary, and the remaining 1 Tbs. In a small bowl, mix the mustard, garlic, thyme, rosemary, and the remaining 1 Tbs. salt and 1 tsp. pepper. Spread all over the lamb, transfer to a large nonreactive dish, cover, and refrigerate for at least 24 hours and up to 2 days.

Just before grilling, make the sauce:

• In a medium bowl, whisk 1/4 cup water with the sugar, salt, and pepper.they don’t have to dissolve completely. Stir in the mint, vinegar, and oil. Let sit while the lamb grills. Taste and season with more sugar, salt, and pepper if needed. (The sauce should have a sharp, acidic tang to complement the rich lamb.)

Grill the lamb:

• Heat a gas grill to medium high or prepare a charcoal fi re with hot and medium-hot areas. Put the lamb on the grill (on the hotter part if using a charcoal fire) and cook (covered on a gas grill) without disturbing it until it’s nicely browned, 6 to 8 minutes. Flip, reduce the heat on the gas grill to medium (or move to the cooler part of the charcoal fire), and cook until an instant-read thermometer inserted into a thicker part of the lamb registers 130°F for medium rare, 5 to 8 more minutes.
• Transfer the lamb to a cutting board, tent with foil, and let rest for 10 minutes. Slice thinly across the grain. and serve with the mint sauce.

Serve with Chopped Tomato & Cucumber Salad with Mint & Feta.

Look for a spicy Shiraz blend such as the Peter Lehmann “Clancy’s,” Barossa Valley.

Stuff leftover lamb and tomato-cucumber salad (see serving suggestion, above) into a pita for sandwiches.