Prep the lamb by removing any butcher’s twine and slicing through the thickest parts of the leg to make one uniform cut. You can ask your butcher to do this for you if you’d like. The night before you plan to grill, combine lamb, yogurt, garlic, chili flakes and pepper in a gallon-sized freezer bag. We don’t salt the lamb until it’s time to grill. Marinate the lamb in the refrigerator overnight.
When it’s time to grill, heat your grill/smoker to 350°F. Place the lamb in the center rack and season with salt. Depending on the thickness of your cut, grill 7-9 minutes per side for medium. Once you flip the meat, add asparagus to the grill and cook alongside the meat while it finishes. Remove meat and asparagus at the same time. Dress asparagus with pesto and season with salt after cooking.
While the lamb cooks, prepare your sauces.
In the work bowl of your food processor, combine all herbed yogurt ingredients and pulse until chopped and smooth. Spoon yogurt into a dish. Give the mixer a quick rinse and prepare the pesto in the same way. Place all ingredients into the food processor, pulse several times, and taste for seasoning. These sauces can be done in advance, but they get better as time goes on. Both sauces last 3-4 days in the refrigerator. To serve, slice the lamb against the grain and serve with sauce and asparagus.