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Au Gratin Potatoes

Au gratin potatoes with thin sliced Yukon golds baked in a garlicky cream sauce until tender, then finished with a bubbling golden cheese crust. French-inspired layering creates creamy, cohesive slices with a rich cheddar–Gruyère top.
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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: 520
Ingredients Equipment Method Notes

Ingredients
  

Potatoes
  • 3 lb Yukon gold potatoes peeled and sliced 1/8 inch thick
Sauce base
  • 3 tbsp butter
  • 3 cloves garlic 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 (use 1 cup in the sauce, and the remaining for topping)
  • 1 cup shredded Gruyere divided (use 1/2 cup in the sauce, and the remaining for topping)

Equipment

  • 1 sheet pan

Method
 

Prep and preheat
  1. Preheat the oven to 375F. Butter a 9x13-inch baking dish.
Make the creamy sauce
  1. Melt the butter, then cook the minced garlic for 30 seconds. Keep it gently sizzling so the garlic turns fragrant without browning.
  2. Whisk in the all-purpose flour and cook for 1 minute. Stir constantly until the mixture looks smooth and lightly cooked.
  3. Slowly whisk in the whole milk and heavy cream. Simmer until the sauce thickens enough to coat the back of a spoon.
  4. Season the thickened sauce with salt, black pepper, and fresh thyme leaves. Turn off the heat as soon as the seasoning is fully incorporated.
  5. Remove from the heat and stir in 1 cup shredded sharp cheddar and 1/2 cup shredded Gruyere. Mix until the cheese fully melts and the sauce looks glossy.
Layer and bake
  1. Layer a third of the sliced Yukon gold potatoes in the baking dish and spoon over a third of the sauce. Spread evenly so the potatoes are well coated.
  2. Repeat the layering with a second third of the potatoes and a second third of the sauce. Press the top layer down lightly for even baking.
  3. Add the final third of the potatoes and pour over the remaining sauce. Sprinkle the remaining shredded sharp cheddar and shredded Gruyere over the top.
  4. Cover with foil and bake at 375F for 45 minutes. The edges should be bubbling when you check through the foil.
  5. Uncover and bake at 375F for 25 to 30 minutes until golden and tender. Look for a bubbling, browned cheese crust on top.
Rest and serve
  1. Rest the au gratin potatoes for 15 minutes before serving. The layers will set slightly for cleaner slices.

Notes

Pro tip: slice the Yukon gold potatoes to 1/8 inch thickness for the most even, creamy texture throughout. Refrigerate leftovers in a covered container for up to 3 days and reheat in a 350F oven until warmed through. Freezing is not recommended because the creamy sauce can break when thawed. For a lighter option, use 2% milk plus an equal amount of half-and-half in place of whole milk and heavy cream.