Stacked Potato and Leek Gratin

Preheat oven to 375°F (190°C).

In a sauté pan over medium heat, melt the butter. Add the sliced leeks and minced garlic.

Sauté until the leeks are fully cooked and softened, then set aside.

Thinly slice the potatoes to about 1/8-inch thickness using a knife or mandoline.

In a large mixing bowl, combine the sliced potatoes, heavy cream, kosher salt, black pepper, fresh thyme leaves, and onion powder.

Add about 1/2 cup of the grated Parmesan cheese and all of the grated Emmental cheese to the bowl.

Add the cooked leek mixture and toss everything together until the potatoes are evenly coated.

Create small stacks of the coated potato slices and arrange them vertically in a baking dish, packing them in tightly.

Pour any remaining cream and cheese mixture from the bowl over the top of the potatoes.

Cover the baking dish tightly with aluminum foil.

Bake for 1 hour and 15 minutes, or until the potatoes are tender.

Remove the dish from the oven and carefully remove the foil. Increase the oven temperature to 425°F (220°C).

Sprinkle the remaining grated Parmesan cheese over the top.

Return to the oven uncovered and bake for another 10-15 minutes, until golden brown and bubbly.

Let the gratin cool slightly before serving.