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Au Gratin Potatoes

Au gratin potatoes bake thinly sliced russet potatoes in a creamy sharp cheddar sauce until tender beneath a golden top. A final uncovered bake gives the cheese a browned finish, while a 10-minute rest helps the layers set.
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Prep Time 20 minutes
Cook Time 1 hour 20 minutes
Resting 10 minutes
Total Time 1 hour 50 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 430
Ingredients Equipment Method Notes

Ingredients
  

For the potatoes
  • 1 tbsp butter unsalted, softened, for greasing
  • 2 lb potatoes russet, peeled and sliced 1/8 inch thick
For the cheese sauce
  • 3 tbsp butter unsalted
  • 3 tbsp all-purpose flour
  • 2 cups whole milk
  • 1 cup heavy cream
  • 1 tsp kosher salt
  • 0.5 tsp black pepper
  • 0.25 tsp garlic powder
  • 2 cups sharp cheddar cheese shredded and divided

Equipment

  • 1 9x13-inch baking dish

Method
 

Prepare the potatoes
  1. Heat the oven to 375°F and grease a 9x13-inch baking dish with the softened butter.
  2. Peel and slice the potatoes 1/8 inch thick.
Make the cheese sauce and bake
  1. Melt the butter in a medium saucepan over medium heat, whisk in the flour, and cook for 1 minute.
  2. Gradually whisk in the milk and cream until smooth.
  3. Whisk in the salt, pepper, and garlic powder.
  4. Cook, stirring, until the sauce thickens enough to coat the back of a spoon, about 5 minutes.
  5. Remove the saucepan from the heat and stir in 1 1/2 cups of the cheddar until melted.
  6. Arrange half of the potatoes in the baking dish and pour over half of the cheese sauce.
  7. Layer in the remaining potatoes and sauce, then sprinkle the remaining 1/2 cup cheddar over the top.
  8. Cover the dish tightly with foil and bake for 45 to 55 minutes.
  9. Uncover and bake for 20 to 25 minutes, until the top is golden and a knife slides easily into the potatoes at the center.
  10. Let the potatoes rest for 10 minutes before serving.

Notes

Slice the potatoes evenly so they cook at the same rate. Refrigerate leftovers for 3 to 4 days; freezing is not recommended because the cream sauce may separate. For a gluten-free swap, use gluten-free all-purpose flour.