• Preheat oven to 350°F. Butter or spray a 9×13” baking dish.
• In a large frying pan, melt the butter over medium heat. Add the leeks and cook, stirring occasionally, until tender, about 7 minutes. Remove from the heat.
• Peel the potatoes and slice into ¼” thick rounds. If you have a mandolin – it’ll go much faster and the potatoes will be the same thickness for more even cooking.
• Now just make 3 layers of potato, salt and pepper, leek and gruyere: A layer of potatoes spread in an even layer in the baking dish, sprinkle with salt and pepper, spread 1/3 of the leek mixture over that, followed by 1/3 of the cheese. Repeat for the other 2 layers.

Next: Heat the half ‘n half, pour and bake 90-minutes

• In a small saucepan, heat the half ‘n half over medium-high heat until it is simmering. Pour the hot cream evenly over the potatoes. Cover tightly with aluminum foil and place the dish on a rimmed baking sheet just in case there’s any bubbling over! We don’t want a mess on Thanksgiving, right?!
• Bake for 1 hour. Remove the foil and let it bake a little more – until the potatoes are tender and the top is golden brown! Usually about 30 minutes more (about 90-minutes total baking time). Let it stand for about 5 minutes, while you gather everyone to the table. Enjoy! You can run it all off tomorrow 😉