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A blue oval casserole dish containing creamy Scalloped Potatoes with a crispy golden-brown crumb topping and rosemary sprigs.

Ultimate Creamy Pour-Over Potato Gratin

Layers of thinly sliced potatoes baked in a rich, velvety cheese sauce until golden and bubbly, this casserole is the ultimate comfort food. Perfect as a hearty side or a standalone vegetarian main dish.
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Prep Time 25 minutes
Cook Time 1 hour
Total Time 1 hour 25 minutes
Servings: 8 servings
Course: Main Course, Side Dish
Cuisine: American, Comfort Food
Calories: 450
Ingredients Equipment Method Notes

Ingredients
  

For the Potatoes
  • 3 lbs Russet or Yukon Gold potatoes peeled and thinly sliced (approx. 1/8-inch thick)
For the Creamy Cheese Sauce
  • 4 tbsp Unsalted butter melted
  • 4 tbsp All-purpose flour
  • 3 cups Whole milk warmed
  • 1/2 cup Heavy cream
  • 1 tsp Garlic powder
  • 1/2 tsp Onion powder
  • 1/4 tsp Ground nutmeg
  • 1 tsp Salt or to taste
  • 1/2 tsp Black pepper or to taste
  • 2 cups Shredded sharp cheddar cheese
  • 1 cup Shredded Gruyere cheese
For Topping (Optional)
  • 1/2 cup Extra shredded cheese blend
  • 2 tbsp Fresh parsley or chives chopped, for garnish

Equipment

  • 9x13 inch (23x33 cm) baking dish
  • Large saucepan or Dutch oven
  • Whisk
  • Sharp knife or mandoline slicer
  • Large mixing bowl

Method
 

Prepare the Potatoes
  1. Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch (23x33 cm) baking dish.
  2. Peel the potatoes and slice them very thinly, about 1/8-inch thick. A mandoline slicer works best for uniform slices, but a sharp knife can also be used. Place the sliced potatoes in a large bowl and set aside.
Make the Creamy Cheese Sauce
  1. In a large saucepan or Dutch oven over medium heat, melt the butter. Add the all-purpose flour and whisk constantly for 1-2 minutes to create a roux. It should be light golden and smell slightly nutty.
  2. Gradually whisk in the warmed milk and heavy cream, a little at a time, ensuring no lumps form. Continue to whisk until the sauce begins to thicken, about 5-7 minutes.
  3. Stir in the garlic powder, onion powder, ground nutmeg, salt, and black pepper.
  4. Remove the saucepan from the heat. Add 1.5 cups of the shredded sharp cheddar cheese and all of the Gruyere cheese to the hot sauce. Stir until the cheeses are completely melted and the sauce is smooth and creamy. Taste and adjust seasonings if necessary.
Assemble the Casserole
  1. Add the sliced potatoes directly into the creamy cheese sauce in the saucepan. Gently toss the potatoes with the sauce until every slice is thoroughly coated.
  2. Carefully transfer the coated potatoes and sauce into the prepared baking dish, spreading them evenly.
  3. If desired, sprinkle the remaining 1/2 cup of shredded sharp cheddar cheese or the extra shredded cheese blend over the top for a golden crust.
Bake and Serve
  1. Cover the baking dish loosely with aluminum foil. Bake for 40 minutes.
  2. Remove the foil and continue baking for another 20-30 minutes, or until the potatoes are tender when pierced with a fork and the top is golden brown and bubbly. If the top browns too quickly, you can re-cover loosely with foil.
  3. Let the casserole rest for 10-15 minutes before serving to allow the sauce to set. Garnish with fresh parsley or chives, if using.

Notes

For a slightly faster cook time, you can par-boil the potato slices for 5-7 minutes before assembling, then reduce the initial covered baking time to 25-30 minutes.
Feel free to experiment with other cheeses like Monterey Jack, Provolone, or Parmesan.
This casserole can be assembled a day ahead, covered, and refrigerated. Bring to room temperature before baking, and add an extra 10-15 minutes to the covered baking time.
Leftovers store well in an airtight container in the refrigerator for up to 3-4 days.