Roast Leg of Lamb with Yukon Potato Soufflé & Onion Gravy

Preparation

1. Pat the lamb leg dry with paper towels and set aside.
2. Combine the salt, sumac, fennel seeds, ground chiles, black pepper, cinnamon, clove, oregano, and rosemary in a small bowl and stir to combine. Add the olive oil and stir to make a thick paste. Rub the paste over the entire lamb leg, making certain to coat all of the surfaces.
3. Place the rub-coated lamb leg on the rack of a roasting pan with foil on the bottom. Refrigerate the leg for 2 to 3 hours, or allow to sit at least 30 minutes at room temperature. Thirty minutes before you’re ready to roast the lamb leg, heat the oven to 450°.
4. Put the roasting pan with the lamb leg on a rack in the middle of the oven and roast for 15 minutes. Reduce the temperature to 325° and continue to roast until a meat thermometer inserted in the center of the roast registers 140° for medium-rare. Plan on 25 to 30 minutes per pound, or a total of approximately 2 1/2 hours for a 5 to 6 pound leg. Begin checking the temperature after 1 1/2 hours, to get a sense of how quickly the meat is cooking.
5. When it reaches 140°, remove the lamb leg from the oven and pour 1/2 cup water in the bottom of the pan. Cover the lamb leg loosely with foil and let stand 15 to 20 minutes before slicing.
6. Add the pan drippings to a medium-size saucepan and warm over medium-high heat. When the dripping and fat are hot, add the onions and sauté the onions until soft and caramelized, about 10 minutes.
7. Add the butter and flour, reduce the heat to medium and cook stirring constantly for 3 minutes. Add the wine and bring the mixture to a simmer. Reduce the total volume of liquid by half, then add the chicken stock. Bring the mixture to a gentle simmer and cook until it has reduced slightly and thickened to the consistency of gravy.
8. Heat the oven to 400°. Generously butter a round soufflé dish or casserole that is approximately 4” deep and 10” in diameter. Set aside.
9. Place the potatoes in a large pot filled with cold water. Season generously with salt. Bring the water to a boil, reduce to a simmer and cook the potatoes until fork tender, about 15 minutes depending on size.
10. Pour the potatoes into a colander and shake to remove as much moisture as possible. Place the potatoes in a food mill or a potato ricer and add them back to the pot with the butter and flour. Cook the mixture over low heat, stirring constantly with a wooden spoon. The mixture should come together into a single, cohesive mass.
11. Transfer the potato mixture to the bowl of an electric stand mixer fitted with the paddle attachment. Mix on low speed for about 30 seconds while you crack the eggs into a liquid measure. Lightly whisk the eggs and slowly add to the potatoes with the mixture running. Increase the speed to medium when all of the eggs have been added. Mix 1 minute or until the eggs are fully incorporated and the mixture is smooth.
12. Scrape the contents of the mixer bowl into the prepared baking dish and place on rack in the middle of the oven. Bake until the soufflé has nearly doubled in size and is golden brown, 30 to 40 minutes. Serve immediately.