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Au Gratin Potatoes

Au Gratin Potatoes with thin, creamy layers and a bubbling golden cheese crust made in a French-inspired oven bake. Potatoes are layered with a thickened milk-and-cream sauce and finished with cheddar and Gruyère.
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Prep Time 25 minutes
Cook Time 1 hour 15 minutes
Resting 15 minutes
Total Time 1 hour 55 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: French-inspired
Calories: 540
Ingredients Equipment Method Notes

Ingredients
  

Potatoes and cheese layers
  • 3 lb Yukon gold potatoes peeled and sliced 1/8 inch thick
  • 3 tbsp butter
  • 3 garlic cloves minced
  • 3 tbsp all-purpose flour
  • 2 cup whole milk
  • 1 cup heavy cream
  • 1.5 tsp salt
  • 0.5 tsp black pepper
  • 1 tsp fresh thyme leaves
  • 2 cup shredded sharp cheddar divided
  • 1 cup shredded Gruyere divided

Equipment

  • 1 sheet pan
  • 1 Dutch oven

Method
 

Prep and heat
  1. Preheat the oven to 375F and butter a 9x13-inch baking dish.
  2. Melt the butter, then cook the minced garlic for 30 seconds.
  3. Whisk in the all-purpose flour and cook for 1 minute.
Make the creamy sauce
  1. Slowly whisk in the whole milk and heavy cream, then simmer until thickened.
  2. Season the sauce with salt, black pepper, and fresh thyme leaves.
  3. Remove from the heat and stir in 1 cup shredded sharp cheddar and 1/2 cup shredded Gruyere.
Layer and bake
  1. Layer a third of the potatoes in the baking dish, then spread a third of the sauce over the top.
  2. Repeat layering two more times, then top with the remaining cheese.
  3. Cover with foil and bake for 45 minutes.
  4. Uncover and bake for 25 to 30 minutes, until golden and tender.
  5. Rest for 15 minutes before serving.

Notes

For the smoothest layers, keep the potato slices close to 1/8 inch so they soften evenly while baking. Refrigerate leftovers in an airtight container up to 4 days; reheat covered in a 325F oven until warmed through. Freezing is not recommended because the cream sauce can break when thawed. If you need a lighter option, use half-and-half instead of the heavy cream and expect a slightly less thick sauce.