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Creamy Au Gratin Potatoes

Creamy au gratin potatoes layer thin russet potato rounds under a cheddar cheese sauce and bake until tender. A final uncovered bake gives the top a golden finish, with a 15-minute rest before serving.
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Prep Time 20 minutes
Cook Time 1 hour 25 minutes
Resting 15 minutes
Total Time 2 hours
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 525
Ingredients Equipment Method Notes

Ingredients
  

For the potatoes
  • 1 tbsp nonstick cooking spray
  • 3 lb russet potatoes peeled
For the cheese sauce
  • 4 tbsp unsalted butter
  • 0.25 cup all-purpose flour
  • 2 cloves garlic minced
  • 3 cups whole milk
  • 1 tsp kosher salt
  • 0.5 tsp ground black pepper
  • 2 cups sharp cheddar cheese shredded, divided

Equipment

  • 1 9x13-inch baking dish

Method
 

Prepare the potatoes
  1. Heat the oven to 350°F.
  2. Coat a 9x13-inch baking dish with cooking spray.
  3. Slice the potatoes into 1/8-inch-thick rounds.
  4. Arrange the potatoes in overlapping layers in the prepared dish.
Make the cheese sauce
  1. Melt the butter in a medium saucepan over medium heat.
  2. Add the garlic and cook for 30 seconds.
  3. Whisk in the flour and cook for 1 minute.
  4. Gradually whisk in the milk, salt, and pepper until smooth.
  5. Bring the sauce to a gentle simmer, whisking often.
  6. Cook for 3 to 5 minutes until thick enough to coat the back of a spoon.
  7. Remove the sauce from the heat and stir in 1 1/2 cups of the cheddar until melted.
Bake the gratin
  1. Pour the cheese sauce evenly over the potatoes.
  2. Cover the dish tightly with foil.
  3. Bake for 50 to 60 minutes, until a knife slides easily into the potatoes.
  4. Remove the foil and sprinkle the remaining 1/2 cup cheddar over the top.
  5. Bake uncovered for 20 to 25 minutes, until the top is golden and the potatoes are tender.
  6. Rest for 15 minutes before serving.

Notes

Slice the potatoes evenly so they cook at the same rate. Store leftovers covered in the refrigerator for 3 to 4 days; freezing is possible, though the sauce texture may change. For a gluten-free variation, use a gluten-free all-purpose flour blend in place of the all-purpose flour.