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Au Gratin Potatoes

Au gratin potatoes with thin, 1/8-inch slices baked in a rich garlic cream sauce until tender and bubbling under a golden cheese crust. Layered for creamy, cohesive wedges in every serving.
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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: 680
Ingredients Equipment Method Notes

Ingredients
  

Potatoes
  • 3 lb Yukon gold potatoes peeled and sliced 1/8 inch thick
Sauce
  • 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
Cheese
  • 2 cup shredded sharp cheddar divided
  • 1 cup shredded Gruyere divided

Equipment

  • 1 sheet pan

Method
 

Prep and preheat
  1. Preheat the oven to 375F, then butter a 9x13-inch baking dish so the potatoes release cleanly.
Make the creamy sauce
  1. Melt the butter, cook the minced garlic for 30 seconds, then whisk in the all-purpose flour and cook for 1 minute until smooth.
  2. Slowly whisk in the whole milk and heavy cream, then simmer until thickened with a silky coating consistency.
  3. Season with salt, black pepper, and fresh thyme leaves, then keep the sauce hot and cohesive.
  4. Remove from the heat and stir in 1 cup of shredded sharp cheddar and 1/2 cup of shredded Gruyere until melted.
Layer and bake
  1. Layer one-third of the sliced Yukon gold potatoes in the baking dish, then spoon over one-third of the sauce.
  2. Repeat the layering process two more times, then finish by topping with the remaining shredded sharp cheddar and shredded Gruyere.
  3. Cover with foil and bake for 45 minutes, until the potatoes are mostly tender and the edges look set.
  4. Uncover and bake for 25 to 30 minutes at 375F until golden on top and the potatoes are tender when pierced.
Rest and serve
  1. Rest the au gratin potatoes for 15 minutes before serving so the creamy layers thicken and slice cleanly.

Notes

For the smoothest sauce, whisk the milk mixture in slowly so there are no flour lumps, and simmer only until it turns thick enough to coat the back of a spoon. Refrigerate leftovers in an airtight container up to 4 days; reheat covered in a 325F oven until hot. Freezing is not recommended because the dairy can separate after thawing. If you want a lighter option, use half-and-half in place of the heavy cream for a slightly less rich texture.