- 1 4-pound boneless leg of lamb
- Olive oil
- 1 bulb garlic, chopped
- 1/4 cup rosemary, chopped
- Zest of 2 lemons
- Kosher salt and pepper
- 4 pounds (6-7 large) russet potatoes, peeled and sliced 1/8-inch thick
- Olive oil, for liberal drizzling, about 1/2 cup
- Salt and pepper
- 4 tablespoons rosemary, chopped
- 4 tablespoons butter
- 4 large or 6 small onions
- 1 bulb garlic, cloves cracked from skin and thinly sliced
- 1 1/2 to 2 cups loosely packed grated Parmigiano-Reggiano cheese
- 2 28- to 32-ounce cans San Marzano tomatoes, lightly drained
- A handful basil leaves, torn
Heat oven to 450F with rack placed in the center of the oven.
Coat lamb in olive oil and slather with chopped garlic, rosemary and lemon zest. Lightly salt and aggressively season with black pepper.
Roast to brown 15 minutes then reduce heat to 325F and roast 1 1/4 hours until a meat thermometer reads 130F (for rare) or 1 1/2 hours until an internal temperature of 140F for medium-rare once meat has rested. Remove net and thinly slice.
While the lamb roasts, slice potatoes, adding them to a bowl of salted cold water as you go. Once all of the potatoes are sliced, drain and add them to a large bowl. Dress lightly with olive oil; season with rosemary and pepper.
Heat a large pan over medium heat with a drizzle of olive oil and melt butter into it. Add onions and garlic, and season with salt, pepper and bay. Cook until lightly golden and soft, 30 minutes, stirring frequently.
Hand-crush the tomatoes and combine with basil in a large bowl.
Arrange 1/3 of the potatoes in shingled layer in a large casserole dish, sprinkle with 1/3 of the cheese, top with half the onions then layer in half the tomatoes. Repeat, topping the casserole with the last third of the potatoes and cheese. Place in the oven alongside the lamb at 325F. for 45 minutes. When you remove the lamb, transfer potatoes to upper third of oven and lightly broil to brown cheese.