Potatoes Au Gratin

5 from 6 votes

The best Potatoes Au Gratin recipe combines thinly sliced potatoes and a creamy flavorful cheese sauce that gets baked to perfection with a crispy top.

Prep Time20

Cook Time55

Total Time1 15

Course: Side Dish

Cuisine: American

Servings: servings

Author: Krissy Allori

Equipment

Ingredients

3 pounds golden potatoes lightly scrubbed, skin on, and sliced thin, see note
1 medium yellow onion peeled and sliced thin
4 tablespoons unsalted butter
4 tablespoons all-purpose flour
2 cups whole milk
4 cloves roasted garlic smashed into paste
1 teaspoon dry mustard
1/4 teaspoon nutmeg freshly grated
2 cups cheddar cheese shredded (I used a cheddar gruyere blend)
1 teaspoon Kosher salt or more, to taste
1/2 teaspoon pepper freshly ground

Instructions

Preheat oven to 400 degrees F.
Wash potatoes and slice into thin slices. Soak in large bowl of cold water for at least an hour.
Melt butter in a sauce pan and add sliced onion. Stir to coat in butter and then allow to cook, undisturbed, until the onion starts to brown. Add the flour and cook 2-3 minutes, stirring constantly to avoid burning. You want mixture to smell like a cooked pie crust. Add milk and whisk over medium heat until thick and bubbly. Remove from heat and stir in roasted garlic, dry mustard, nutmeg, and cheese until melted.
Place potato slices upright in a greased casserole dish. Sprinkle with salt and pepper. Spoon cheese sauce over potatoes.
Cover with greased lid or foil and bake 35 minutes, covered. Remove cover and bake an additional 20-30 minutes or until lightly browned and potatoes are cooked.

Notes

A mandolin is the easiest way to get super thin sliced potatoes.
The thinner your potatoes, the faster they will cook. If you do not slice with a mandolin, you may have to increase your cooking time. Likewise, if potatoes are not of uniform thickness, the thin slices will cook much faster than the thick slices.

Nutrition