Classic Potatoes Au Gratin

This Potatoes Au Gratin recipe is a cozy, indulgent side dish with layers of tender red potatoes and onions smothered in a creamy, cheesy sauce. Featuring sharp cheddar and rich Gruyere, each bite is packed with bold flavors, creamy textures, and a perfect golden crust. This dish is the ultimate comfort food, ideal for special dinners, holidays, or anytime you crave a comforting, cheesy potato dish.

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Ingredients

• 2 ½ pounds red potatoes
• 1 onion, thinly sliced
• 3 tablespoons butter
• 3 tablespoons all-purpose flour
• 1 teaspoon dry mustard powder
• 2 cups milk
• 1 cup shredded cheddar cheese
• ½ cup shredded Gruyere cheese
• ¾ teaspoon salt, divided
• ½ teaspoon black pepper, divided

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Instructions

1. Prepare the Ingredients

• Preheat oven to 400°F. Grease a 2.5 to 3-quart casserole dish.
• Wash potatoes thoroughly and slice them into ⅛-inch thin rounds. Thinly slice the onion.

1. Season and Layer the Potatoes and Onion

• Toss the potato and onion slices with ½ teaspoon of salt and ¼ teaspoon of pepper to coat evenly. Stack the potato slices with onion pieces and place the stacks upright in the casserole dish.

1. Make the Cheese Sauce

• In a saucepan over medium heat, melt the butter, then add flour. Cook for 2 to 3 minutes, stirring constantly to create a roux. Stir in mustard powder, ¼ teaspoon salt, and ¼ teaspoon pepper. Gradually add milk, whisking continuously until the sauce thickens and bubbles.
• Remove the saucepan from heat and stir in the cheddar and Gruyere until smooth and melted.

1. Assemble and Bake

• Pour the cheese sauce over the potatoes, gently separating them to allow the sauce to seep between the layers. Cover the dish with foil (sprayed with cooking spray to prevent sticking).
• Bake for 60 minutes. Remove foil and bake for an additional 20 to 30 minutes, or until the top is golden and the potatoes are tender. Cool for 15 minutes before serving.

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Tips for the Perfect Potatoes Au Gratin

• Uniform Slicing: Use a mandoline if available for even slices, ensuring consistent cooking.
• Cheese Choice: While cheddar and Gruyere offer a rich flavor, you can substitute with Swiss or Monterey Jack for different flavor profiles.
• Resting Time: Allow the dish to cool briefly before serving to let the sauce thicken and set, making for easier slicing and serving.

Enjoy this comforting, delicious dish alongside your favorite main courses, or serve it as a centerpiece at holiday gatherings!