Golden Yukon Potato Gratin

1. Preheat Oven and Prepare Baking Dish

Adjust your oven rack to the middle position and preheat the oven to 450°F. Grease a 13x9-inch baking dish and set it aside.

2. Cook Potatoes

Place your peeled and sliced potatoes in a large saucepan and cover them with cold water by about an inch. Bring the water to a simmer over medium-high heat, then adjust the heat to maintain a gentle simmer. Cook the potatoes until they are tender, about 18 to 22 minutes. Drain them in a colander.

3. Prepare Half-and-Half Mixture

While the potatoes are cooking, combine the half-and-half with the 3 egg yolks, 1.75 teaspoons of salt, 0.5 teaspoons of pepper, and a pinch of nutmeg in a bowl. Stir this mixture well and set it aside.

4. Process and Mash Potatoes

Once the potatoes are drained, place the empty saucepan over low heat. Using a ricer or food mill, process the potatoes back into the saucepan in batches. Stir in 8 tablespoons of the melted butter until everything is well combined and the potatoes are smooth and fluffy.

5. Combine Potato Mixture

Gradually stir the half-and-half mixture into the mashed potatoes until fully combined. Transfer the potato mixture into the prepared baking dish, smoothing it into an even layer with a rubber spatula.

6. Prepare Egg White Mixture

In a small bowl, combine the egg white with the remaining 2 tablespoons of melted butter and a pinch of salt. Beat this with a fork until it is well mixed. Pour this egg white mixture over the smoothed potatoes, tilting the dish to ensure it covers the surface evenly. Using a paring knife, make a crosshatch pattern on top of the potatoes.

7. Bake Gratin

Place the dish in the oven and bake until the top is golden brown, rotating the dish halfway through the baking time, about 25 to 30 minutes. Let the gratin cool for about 20 minutes before serving.