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Scalloped Potatoes

Scalloped potatoes baked in a creamy milk-and-cream sauce, layered with onions, then finished with Parmesan until golden and fork-tender. Each layer stays tender with a set, lightly thickened sauce for clean slices from a 9x13-inch dish.
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Prep Time 25 minutes
Cook Time 1 hour 30 minutes
Rest 15 minutes
Total Time 2 hours 10 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 540
Ingredients Equipment Method Notes

Ingredients
  

Russet potatoes
  • 3 lb russet potatoes peeled and sliced 1/8 inch thick
Onion
  • 1 onion thinly sliced
Butter
  • 4 tbsp butter
Garlic
  • 3 cloves garlic minced
All-purpose flour
  • 0.25 cup all-purpose flour
Whole milk
  • 3 cup whole milk
Heavy cream
  • 1 cup heavy cream
Salt
  • 2 tsp salt
Black pepper
  • 0.5 tsp black pepper
Fresh thyme leaves
  • 1 tsp fresh thyme leaves
Parmesan
  • 0.5 cup grated Parmesan

Equipment

  • 1 sheet pan
  • 1 Dutch oven

Method
 

Prep and preheat
  1. Preheat oven to 375F and butter a 9x13-inch baking dish with butter, so the potatoes release easily.
Make the creamy sauce
  1. Melt butter in a Dutch oven and cook garlic for 30 seconds, until fragrant (do not brown).
  2. Whisk in all-purpose flour and cook for 1 minute to remove the raw flour taste, stirring continuously.
  3. Gradually whisk in whole milk and heavy cream, then simmer until slightly thickened, with a steady bubble and a coating texture.
  4. Season the sauce with salt, black pepper, and fresh thyme leaves, stirring until the herbs are evenly distributed.
Layer and bake
  1. Layer russet potatoes and onion in the dish in three layers, arranging them evenly for consistent tenderness.
  2. Pour sauce over each layer so the potatoes are well coated, then spread lightly to cover any dry spots.
  3. Cover with foil and bake for 1 hour, until the edges look set and bubbling starts near the sides.
  4. Uncover, sprinkle grated Parmesan evenly over the top, and bake 25-30 minutes until golden and fork-tender.
Rest and serve
  1. Rest the scalloped potatoes for 15 minutes before serving so the sauce thickens and slices hold their shape (steam should subside).

Notes

Pro tip: slice potatoes to about 1/8 inch so they bake evenly and stay tender without needing extra time. Store leftovers in the refrigerator up to 4 days; reheat covered at 325F until hot throughout. Freezing is not ideal because the creamy sauce can loosen after thawing. For a lighter option, use half-and-half instead of the heavy cream (texture will be slightly less rich).