PREHEAT oven to 425°F.
PLACE the potatoes, or sweet potatoes, in a large saucepot and cover with water. Bring to a boil over medium-high heat, until the potatoes are fork tender. About 8-10 minutes.
DRAIN the potatoes and place back into the pot. Add 2 tablespoons of the butter, 2 tablespoons of the heavy cream and 1 teaspoon of the salt. Mash with a potato masher, ricer or electric mixer until smooth and creamy. Set aside.
While the potatoes are boiling, BROWN the ground meat. Place the lamb or beef in a large sauté pan over medium-high heat. Season with 1 teaspoon kosher salt and ½ teaspoon black pepper. Cook, stirring and breaking the meat into small chunks until well browned, about 7 minutes.
PLACE the meat in the ALCAN® Non-Stick Pie Pan, and set aside.
WIPE the sauté pan of excess grease, leaving a thin layer just to coat the pan. Add the onions, carrots, celery and garlic, and sauté until the onions are translucent, about 5 minutes. Season with the remaining 1 teaspoon kosher salt and ½ teaspoon black pepper. Add to the bakeware on top of the meat. (You can mix the meat and vegetables together if desired).
In the same pan, MELT 1 tablespoon of butter, add the mushrooms and sauté until soft, about 5 minutes. Make a well in the centre of the pan, add the remaining 1 tablespoon of butter, sprinkle with the flour and stir until it is melted and a paste forms.
POUR the remaining milk or heavy cream over the mushrooms and whisk to smooth out any lumps from the butter/flour mixture. Cook until thick, about 2 minutes. Pour all over the top of the meat and vegetables.
SPREAD the mashed potatoes, or sweet potatoes, over the top of the Shepherd’s Pie place ALCAN® Non-Stick Pie Pan on a non-disposable baking sheet for support and place in the oven until slightly golden brown and heated through, about 15 minutes.
SERVE directly from the disposable bakeware.