If you are using the mustard coating, paint both sides of the meat and refrigerate the meat for at least an hour if possible — overnight is better. Reserve 2 tablespoons for the final cooking. Serves 10-12 (based on 6.5 pound leg)
4-6 pound butteflied leg of lamb
mustard coating and marinade, optional (see recipe below)
BROIL-ROASTING: Brown the lamb slowly under the broiler for 10 minutes on each side. (Ahead of time: After browning, you may let it sit at room temperature for up to an hour.)
Finishing the lamb — about 20 minutes at 375°F. When you are ready to finish it off, set the lamb skin side up and paint with the reserved mustard coating. Roast for 15 to 20 minutes in the upper third of the preheated oven.
When is it done? The lamb is done when the flesh has just achieved a springy texture to the pressure of your finger, in contrast to its squashy feel when raw. Red rare will be 125°F on your meat thermometer; medium pinky rare, 130°F. Remove the meat from the oven and let it sit 10 to 15 minutes before carving so the juices can retreat back in to the tissues.
SERVING: To carve, cut into slanting slices across the grain — not as neat as for a bone-in leg, but carving is easy. Moisten each serving with accumulated pan juices.
COOK’S NOTE: A butterflied leg of lamb cooks in a third the usual time of a whole leg, and is a breeze to carve.
MUSTARD COATING AND MARINADE
2 large cloves of garlic
½ teaspoon salt
2 tablespoons Dijon-style prepared mustard
1 tablespoon soy sauce
1½ teaspoon fragrant ground rosemary, thyme or oregano
2 tablespoons freshly squeezed lemon juice
¼ cup olive oil or peanut oil
Puree the garlic into a small bowl and mash to a paste with the salt. Whisk in the mustard, soy, herbs, lemon juice and then the oil slowly, still whisking, to make a mayonnaise-like cream.
— Adapted from Julia Child, “The Way to Cook”