Go Back

Au Gratin Potatoes

Au gratin potatoes with thin Yukon Gold slices baked in a thickened milk-and-cream sauce for creamy layers and a bubbling golden cheese crust. French-inspired comfort side with a simple roux-based sauce and a tender, sliceable finish.
Print Recipe Pin Recipe
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: 590
Ingredients Equipment Method Notes

Ingredients
  

Potatoes
  • 3 lb Yukon gold potatoes, peeled and sliced 1/8 inch thick
Sauce
  • 3 tbsp butter
  • 3 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
  • 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 easily. Aim for a glossy, even butter coating along the bottom and sides.
Make the sauce
  1. Melt the butter, then cook the minced garlic for 30 seconds until fragrant. Keep it moving so it doesn’t brown.
  2. Whisk in the all-purpose flour and cook for 1 minute. The mixture should look slightly thicker and smell toasted.
  3. Slowly whisk in the whole milk and heavy cream, then simmer until the sauce thickens enough to coat the back of a spoon. Watch for gentle bubbling and a smooth, glossy texture.
  4. Season the sauce with salt, black pepper, and fresh thyme leaves. Stir until evenly speckled with thyme.
  5. Remove from heat and stir in 1 cup cheddar and 1/2 cup Gruyere. Mix until the cheeses fully melt and the sauce looks creamy.
Assemble and bake
  1. Layer one-third of the sliced potatoes in the baking dish, then spoon over one-third of the sauce. Spread the sauce to reach the edges.
  2. Repeat the potato and sauce layering two more times, ending with a final top layer of sauce. Make the top layer even for consistent browning.
  3. Top with the remaining cheddar and Gruyere. You should see a thick cheese layer covering the surface.
  4. Cover with foil and bake for 45 minutes. You’re looking for bubbling around the edges after this stage.
  5. Uncover and bake for 25 to 30 minutes at 375F until golden and tender. The top should be visibly browned and the potatoes should pierce easily.
Rest and serve
  1. Rest for 15 minutes before serving so the layers set and hold together. The sauce will thicken slightly as it cools.

Notes

Pro tip: Slice potatoes to about 1/8 inch for faster, even tenderness so each bite has creamy layers. Refrigerate leftovers in an airtight container up to 3 days; reheat covered in a 325F oven until hot. Freezing isn’t recommended because the dairy sauce can separate after thawing. For a lighter option, use half-and-half in place of some of the heavy cream while keeping the cheese amounts the same.