Ingredients
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3 lbs russet or Yukon Gold potatoes, peeled and thinly sliced
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3 tablespoons unsalted butter
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1 small onion, finely chopped
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3 tablespoons all-purpose flour
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2 ½ cups whole milk or half-and-half
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1 teaspoon salt
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½ teaspoon black pepper
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½ teaspoon paprika
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½ teaspoon garlic powder
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Optional: 1 cup shredded cheddar or Gruyère cheese
Instructions
Preheat oven to 350°F (175°C). Peel and slice potatoes into thin, even rounds (about ⅛-inch thick). Set aside.
In a saucepan over medium heat, melt butter. Add chopped onion and cook until softened and fragrant. Stir in flour and cook for 1 minute to remove the raw flour taste.
Gradually whisk in milk, stirring constantly until the sauce thickens slightly. Add salt, pepper, paprika, and garlic powder. Remove from heat once smooth and creamy.
Grease a baking dish. Layer half of the potatoes evenly in the dish, pour half of the sauce over them, then repeat with remaining potatoes and sauce. Add cheese between layers if using.
Cover with foil and bake for 60 minutes. Remove foil and bake an additional 20–25 minutes, until the top is golden and potatoes are fork-tender. Let rest 10 minutes before serving.
Notes
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Slice potatoes evenly for uniform cooking.
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Use Yukon Gold potatoes for extra creaminess.
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Let the dish rest before serving to allow sauce to thicken.
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Cover tightly during the first bake to prevent drying.