Bits of caramelized roasted garlic define each bite of this stuffed leg of lamb, while a milder mint pesto adds a touch of freshness and saltiness, making this a worthy holiday roast.
Preheat oven to 400°F. Cut top quarters off of heads of garlic. Place garlic cloves, cut side down, in center of a sheet of aluminum foil and drizzle with olive oil. Seal foil and place directly on oven rack. Cook until cloves are browned and very soft, 45-60 minutes. Remove from oven, let cool for 10 minutes, then squeeze cloves out of the skin into a small bowl and mash into a paste with a fork.
Lay leg of lamb open on a large cutting board, fat side down. Season meat generously with salt and pepper. Spread roasted garlic paste over exposed meat. Spread mint pesto on top of garlic. Roll lamb closed and tie securely with butcher twine about every inch. Season outside of lamb generously with salt and pepper.
Light one chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and arrange the coals on one side of the charcoal grate. Set cooking grate in place, cover grill and allow to preheat for 5 minutes. Clean and oil the grilling grate. Sear lamb on hot side of grill until browned all over, about 4 minutes per side. Move to cool side of grill, cover, and let cook until meat registers 130°F on an instant read thermometer inserted into thickest part of lamb. Transfer to a cutting board and let rest for 15 minutes. Slice and serve immediately.