This lamb is so worth the trouble….trust me. It’s not hard to make, really; it’s just a bit fussy since there are a few steps to go through before you can chuck the whole thing into the oven and forget about it for a while. Still, it’s relatively uncomplicated for something that tastes so good and looks so impressive on the table.
1 boneless leg of lamb, approximately 4 lbs., butterflied
2 heads garlic
2 tablespoons dijon mustard
1/4 cup finely chopped fresh rosemary, divided
1 1/2 tablespoons sea salt, divided
2 tsp. freshly ground pepper, divided
1/4 cup olive oil, divided, plus more for roasting the garlic
8 oz. fresh baby spinach leaves
To roast the garlic, cut the tops off of both heads of garlic and set them on a sheet of aluminum foil. Drizzle olive oil over the cut sides of the garlic, wrap tightly in foil, and roast at 400 degrees for about 40 minutes, until the cloves are soft and golden brown. Allow the garlic to cool completely before making the lamb.
Preheat oven to 450 degrees. Squeeze the roasted garlic into a small bowl. Using a fork, mix the roasted garlic cloves with the dijon mustard, 1 tablespoon of rosemary, 1 1/2 tsp. of salt, 1 tsp. of pepper, and 1 tablespoon of olive oil, smashing the cloves of garlic until you have a relatively smooth paste.
Lay the butterflied lamb leg out on a flat surface. Smear the garlic mixture all over the lamb, then lay the spinach leaves all over the entire surface of the meat. Carefully roll the lamb up (it will be a little messy — that’s okay), keeping the spinach and garlic mixture inside the rolled meat. Use kitchen twine to tie the roll in three or four places.
In a small bowl, combine the remaining 1 tablespoon of salt, 1 tsp. pepper, 3 tablespoons of rosemary, and 3 tablespoons of olive oil. Smear the salt mixture liberally over the entire outside surface of the rolled lamb.
Set the lamb in a roasting pan and cook at 450 degrees for 20 minutes; then reduce the heat to 350 and cook for an additional 40 minutes, until the internal temperature registers about 130 degrees (this will give you medium lamb; cook longer if you like it more well done). Remove the lamb from the oven, cover with foil, and allow to rest for 30 minutes to finish cooking and redistribute the juices into the meat.