How to Make It
Preheat the oven to 400°. Toss the bread with 1 1/2 tablespoons of the olive oil. Spread the bread on a baking sheet and toast in the oven for 12 to 15 minutes, until dry and brown.
In a small skillet, warm the remaining 1 1/2 tablespoons olive oil. Add the shallot, pancetta, mortadella and sage and stir over moderate heat until the shallot is soft, about 5 minutes.
In a bowl, combine the toasted bread with the lamb broth and let stand for 5 minutes. Add the pancetta mixture along with the cheese and mix well. Season the stuffing liberally with pepper.
Open the leg of lamb and season the meat with salt and pepper. Spread the stuffing over the meat and then re-form the leg, patting it into an even cylindrical shape. Tie the roast at 1-inch intervals and place in a small roasting pan. Season with salt and pepper.
Roast the leg of lamb on the top shelf of the oven for 1 hour and 10 minutes, basting with the pan juices every 20 minutes. The meat is medium-rare when the internal temperature reaches 125°. Let the roast rest for about 10 minutes, then carve and serve with the pan juices. (If the pan is dry, deglaze it by stirring in approximately 1 cup of water and boiling until the juices are well reduced and flavorful.)