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Au Gratin Potatoes

Au gratin potatoes with thin sliced Yukon Gold layers and a creamy milk-cream sauce, finished with a bubbling golden cheese crust. Baked covered then uncovered at 375°F for tender potatoes and crisp, browned 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: 510
Ingredients Equipment Method Notes

Ingredients
  

Yukon gold potatoes
  • 3 lb Yukon gold potatoes peeled and sliced 1/8 inch thick
Butter
  • 3 tbsp butter
Garlic
  • 3 cloves garlic minced
All-purpose flour
  • 3 tbsp all-purpose flour
Whole milk
  • 2 cup whole milk
Heavy cream
  • 1 cup heavy cream
Salt
  • 1.5 tsp salt
Black pepper
  • 0.5 tsp black pepper
Fresh thyme leaves
  • 1 tsp fresh thyme leaves
Sharp cheddar
  • 2 cup shredded sharp cheddar divided
Gruyere
  • 1 cup shredded Gruyere divided

Equipment

  • 1 sheet pan
  • 1 Dutch oven

Method
 

Preheat and prep
  1. Preheat the oven to 375°F, then butter a 9x13-inch baking dish.
Make the creamy sauce
  1. Melt the butter, then cook the minced garlic for 30 seconds.
  2. Whisk in the all-purpose flour and cook for 1 minute, stirring until smooth.
  3. Slowly whisk in the whole milk and heavy cream, then simmer until the mixture thickens.
  4. Season the thickened sauce with salt, black pepper, and fresh thyme leaves.
  5. Remove from the heat and stir in 1 cup of the shredded sharp cheddar and 1/2 cup of the shredded Gruyere.
Layer and bake
  1. Layer a third of the potato slices in the baking dish, then pour a third of the sauce over the top.
  2. Repeat the layers two more times, ending with the final potato layer.
  3. Top with the remaining sharp cheddar and Gruyere.
  4. Cover with foil and bake for 45 minutes.
  5. Uncover and bake 25 to 30 minutes, until golden and the potatoes are tender, with bubbling cheese on top.
Rest and serve
  1. Rest the au gratin potatoes for 15 minutes before serving so the layers set and slice cleanly.

Notes

Pro tip: slice the potatoes to about 1/8 inch so they bake tender at the same rate—if your slices vary, some may stay firm. Store covered in the fridge up to 4 days; reheat in the oven at 350°F until hot and bubbly. Freeze yes, but texture may soften slightly; thaw in the fridge overnight. For a lighter option, use half-and-half in place of part of the cream and still simmer until thick.