Ingredients
Equipment
Method
- Preheat your oven to 375°F (190°C). Peel the russet potatoes and, using a mandoline slicer or a very sharp knife, slice them into uniform 1/8-inch thick rounds. Place the sliced potatoes in a large bowl of cold water to prevent browning while you prepare the sauce.2.5 lbs Russet Potatoes
- In a large saucepan or Dutch oven, melt 2 tablespoons of unsalted butter over medium heat. Add the finely diced yellow onion and cook, stirring occasionally, until softened and translucent, about 5-7 minutes. Add the minced garlic and dried thyme, and cook for another minute until fragrant.4 tablespoons Unsalted Butter, 1/2 large Yellow Onion, 3 cloves Garlic, 1 teaspoon Dried Thyme
- Sprinkle the 1/4 cup of all-purpose flour over the onion mixture. Cook, stirring constantly, for 1-2 minutes to create a thick paste, or "roux." This will thicken your sauce.1/4 cup All-Purpose Flour
- Slowly whisk in the warmed whole milk and heavy cream, a little at a time, ensuring no lumps form. Continue whisking until the sauce is smooth and starts to thicken, about 3-5 minutes.2 cups Whole Milk, 1 cup Heavy Cream
- Remove the sauce from the heat. Stir in the salt, black pepper, and freshly grated nutmeg. Add 2 cups of the shredded sharp cheddar cheese and 1 cup of the shredded Gruyère cheese (or your chosen blend). Stir until the cheese is completely melted and the sauce is smooth and creamy. Taste and adjust seasoning if necessary.1 teaspoon Salt, 1/2 teaspoon Black Pepper, 1/4 teaspoon Nutmeg, 2 cups Sharp Cheddar Cheese, 1 cup Gruyère Cheese
- Drain the sliced potatoes thoroughly and pat them dry with a clean kitchen towel or paper towels. Grease a 9x13-inch baking dish with the remaining 2 tablespoons of butter. Arrange one-third of the sliced potatoes in an even layer at the bottom of the prepared baking dish. Pour about one-third of the cheese sauce over the potatoes, spreading it evenly.2.5 lbs Russet Potatoes, 4 tablespoons Unsalted Butter
- Repeat the layering process: add another third of the potatoes, followed by another third of the cheese sauce. Finish with the remaining potatoes, then pour the last of the cheese sauce over the top, making sure to cover all the potatoes.2.5 lbs Russet Potatoes
- Cover the baking dish tightly with aluminum foil. Bake for 45 minutes. This initial covered baking helps the potatoes cook through and become tender without browning too quickly.
- Remove the foil. Sprinkle the grated fresh Parmesan cheese over the top. Continue baking, uncovered, for another 20-30 minutes, or until the potatoes are tender (test with a fork) and the top is golden brown and bubbly.1/4 cup Fresh Parmesan Cheese
- Carefully remove the dish from the oven and let it rest for 10-15 minutes before serving. This allows the sauce to set and makes for easier serving. Garnish with fresh chopped parsley if desired.2 tablespoons Fresh Parsley
Notes
Refrigerate leftovers in an airtight container for up to 3-4 days. Can be frozen for 2-3 months. Reheat in oven at 300-325°F (150-160°C).
