The Best Creamy Au Gratin Potatoes Recipe

Preheat oven to 350 degrees F. Prepare a 2-quart gratin dish or a casserole dish by generously rubbing with butter. Place on a lined, high-sided cookie sheet and set aside.

Slice the potatoes into 1/8-inch disks. Toss with salt and pepper. Layer the rounds, slightly overlapping one another, from left to right or in a circle, bottom to top, in the buttered gratin dish.

In a small saucepan, cook the pancetta until crispy, about 3 to 5 minutes. Drain on a paper towel. Set aside.

Cut the cleaned leeks into 1/4-inch strips. In a large skillet over medium heat, melt the butter. Add the leeks, a large pinch of salt, and a few grinds of fresh pepper. Add the thyme. Cook, stirring occasionally, until leeks are tender and golden, 5 to 7 minutes. Discard thyme sprigs and scatter the cooked leeks over the sliced potatoes.

While the leeks are cooking, heat the cream, the stock with the garlic and bay leaf in an additional saucepan. Simmer for about 5 minutes until flavors are infused in the cream. Add nutmeg and white pepper.

Sprinkle half of the pancetta on top of the cooked leeks. Pour the cream over the top. Top with the gruyere. Cover with aluminum foil and bake for 40 to 50 minutes. Uncover and bake until the cheese is bubbling and golden brown, an additional 15 to 20 minutes. Remove from oven, sprinkle with the reserved crispy pancetta and garnish with chopped parsley. Serve.