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Au Gratin Potatoes

Au gratin potatoes with thin sliced Yukon gold layers and a rich milk-cream cheese sauce, baked until bubbling and golden. This French-inspired gratin is cooked covered for tender slices, then uncovered for a crisp, cheesy crust.
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Prep Time 25 minutes
Cook Time 1 hour 15 minutes
rest 15 minutes
Total Time 1 hour 55 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: French-inspired
Calories: 610
Ingredients Equipment Method Notes

Ingredients
  

Potatoes
  • 3 lb Yukon gold potatoes peeled and sliced 1/8 inch thick
Butter
  • 3 tbsp butter
Garlic
  • 3 garlic cloves, minced
Flour
  • 3 tbsp all-purpose flour
Milk and cream
  • 2 cup whole milk
  • 1 cup heavy cream
Seasonings
  • 1.5 tsp salt
  • 0.5 tsp black pepper
  • 1 tsp fresh thyme leaves
Cheese
  • 2 cup shredded sharp cheddar divided (use 1 cup in sauce, reserve 1 cup for top)
  • 1 cup shredded Gruyere divided (use 1/2 cup in sauce, reserve 1/2 cup for top)

Equipment

  • 1 sheet pan

Method
 

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

Notes

Pro tip: Keep potato slices close to 1/8 inch so they cook tender at the same time. Store leftovers covered in the refrigerator up to 4 days; reheat in a 325F oven until steaming. Freezing is not recommended for the best creamy texture. For a lighter swap, use half-and-half in place of the whole milk while keeping the heavy cream for structure and flavor.