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Au Gratin Potatoes

Au gratin potatoes with French-inspired creamy layers of Yukon gold and a bubbling golden cheese crust. Built with a thickened milk-and-cream sauce, baked covered for tender slices, then uncovered until browned.
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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: 620
Ingredients Equipment Method Notes

Ingredients
  

Au gratin potatoes
  • 3 lb Yukon gold potatoes Peeled and sliced 1/8 inch thick.
  • 3 tbsp butter
  • 3 clove 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
  • 2 cup shredded sharp cheddar Divided.
  • 1 cup shredded Gruyere Divided.

Equipment

  • 1 sheet pan
  • 1 Dutch oven

Method
 

Prep and preheat
  1. Preheat the oven to 375°F and butter a 9x13-inch baking dish, coating the bottom and sides evenly.
  2. Set aside sliced Yukon gold potatoes so they’re ready for layering.
Make the creamy sauce
  1. Melt the butter in a Dutch oven over medium heat and cook the minced garlic for 30 seconds until fragrant.
  2. Whisk in the all-purpose flour and cook for 1 minute to form a smooth roux.
  3. Slowly whisk in the whole milk and heavy cream, then simmer until the mixture thickens to a creamy, pourable consistency.
  4. Season the sauce with salt, black pepper, and fresh thyme leaves, stirring to distribute the herbs.
  5. Remove from heat and stir in 1 cup of the shredded sharp cheddar and 1/2 cup of the shredded Gruyere until melted and smooth.
Layer and bake
  1. Layer one-third of the sliced potatoes in the baking dish and spoon one-third of the sauce over top.
  2. Repeat the potato and sauce layers two more times, finishing with the last of the cheese sauce in the dish.
  3. Sprinkle the remaining shredded sharp cheddar and shredded Gruyere over the top for a golden crust.
  4. Cover with foil and bake for 45 minutes, then remove the foil.
  5. Uncover and bake 25-30 minutes more until the potatoes are tender and the top is golden and bubbling.
Rest and serve
  1. Rest the au gratin potatoes for 15 minutes before serving so the creamy layers set and slice cleanly.

Notes

For the smoothest layers, keep potato slices close to 1/8 inch so they finish tender at the same time. Store leftovers covered in the refrigerator up to 3-4 days and reheat at 350°F until hot throughout. Freezing: yes, freeze in portions for up to 2 months, then thaw overnight in the fridge and reheat. For a lighter option, use half-and-half in place of some heavy cream while keeping the sauce thickness by simmering a bit longer.