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Step-by-Step Guide to Perfect Creamy Au Gratin Potatoes

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Ingredients
 

  • Potatoes: 4 large peeled and thinly sliced (Russet or Yukon Gold work well)
  • Onion: 1 small thinly sliced (optional)
  • Butter: 3 tablespoons
  • All-purpose flour: 3 tablespoons
  • Salt: 1 teaspoon
  • Pepper: 1/2 teaspoon
  • Milk: 2 cups whole milk is best for creaminess
  • Cheddar cheese: 1 1/2 cups shredded (you can also use Gruyère for a more traditional flavor)
  • Parmesan cheese: 1/2 cup grated (for the topping)

Instructions

Preheat the Oven:

  • Preheat your oven to 400°F (200°C). Grease a 9x13 inch baking dish or an equivalent.

Layer the Potatoes and Onion:

  • Arrange a layer of potato slices at the bottom of the greased dish. If using onion, add a layer of thinly sliced onions on top of the potatoes. Season with a little salt and pepper. Repeat the layers until all the potatoes and onions are used.

Make the Sauce:

  • In a medium saucepan, melt the butter over medium heat. Stir in the flour, salt, and pepper and cook for 1-2 minutes to form a roux. Gradually whisk in the milk, ensuring there are no lumps. Continue to cook and stir until the sauce has thickened, about 5 minutes.

Add Cheese:

  • Remove the sauce from the heat and stir in 1 cup of the cheddar cheese until the cheese has melted and the sauce is smooth.

Combine:

  • Pour the cheese sauce evenly over the layered potatoes and onions in the baking dish. Use a spatula or the back of a spoon to gently spread the sauce, ensuring it seeps into the layers.

Bake:

  • Cover the dish with aluminum foil and bake in the preheated oven for 60 minutes. After 60 minutes, remove the foil, sprinkle the remaining cheddar cheese and all of the Parmesan cheese over the top, and bake uncovered for an additional 20-30 minutes, or until the top is golden and bubbly, and the potatoes are tender.

Rest and Serve:

  • Let the dish stand for about 10 minutes after removing it from the oven to let the sauce set. This makes serving easier and allows flavors to meld.