- 2 tablespoons unsalted butter, plus more for the dish (30 g)
- Kosher salt
- 3 pounds Yukon gold potatoes, peeled and thinly sliced (1350 g)
- 2 tablespoons all-purpose flour (30 g)
- 1 cup 1% low-fat milk, at room temperature (225 ml)
- 1 cup whole milk, at room temperature (225 ml)
- Freshly ground pepper
- ¼ teaspoon freshly grated nutmeg (0.8 g)
- ¼ cup grated gruyere cheese (0.6 g)
- Preheat the oven to 350° Fahrenheit. Lightly polish a 3-quart baking dish with melted butter.
- Ready a large pot of salted water and boil over medium heat; stir in the potatoes and bring to a simmer until cooked and tender, or for about 8 to 10 minutes. Drain the potatoes fully and return to the pot.
- Meanwhile, in a large deep saucepan, melt 2 tablespoons of butter over medium heat. Mix in the flour with a wooden ladle to make a paste. Stir continuously until the paste puffs slightly, or for about 1 minute.
- Steadily pour in low-fat and whole milk, stirring constantly until thickened, or for about 3 minutes. Remove from heat and sprinkle ½ teaspoon pepper, 1 ½ teaspoons salt, and nutmeg.
- Pour in the sauce over the potatoes and gently toss to coat.
- Transfer the potato mixture to the prepared baking dish and add a little amount of gruyere.
- Bake in the preheated oven until heated through, or for about 10 minutes. Switch the oven to the broiler setting and broil the potatoes until top is browned, or for about 5 minutes. Let it cool for 10 more minutes before serving.
- Serve and enjoy!