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°F.
Wash 3 pounds golden potatoes and slice into thin slices. Soak in large bowl of cold water for at least an hour.
Melt 4 tablespoons unsalted butter in a sauce pan and add 1 medium yellow onion (sliced). Stir to coat in butter and then allow to cook, undisturbed, until the onion starts to brown. Add 4 tablespoons all-purpose flour and cook 2-3 minutes, stirring constantly to avoid burning. You want mixture to smell like a cooked pie crust. Add 2 cups whole milk and whisk over medium heat until thick and bubbly. Remove from heat and stir in 4 cloves roasted garlic (smashed into paste), 1 teaspoon dry mustard, 1/4 teaspoon nutmeg (freshly grated), and 2 cups cheddar cheese until melted.
Place potato slices upright in a greased casserole dish. Sprinkle with 1 teaspoon Kosher salt and 1/2 teaspoon 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