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A delicious Sweet Potato Scalloped Casserole is showcased as the featured image, ready to be served.

BEST Sweet Potato Scalloped Casserole

This Sweet Potato Scalloped Casserole recipe delivers a creamy and flavorful dish by understanding the science of starch gelatinization and balancing sweet and savory flavors. Thinly sliced sweet potatoes are layered in a rich cream sauce with Gruyere and Parmesan cheese, then baked to golden brown perfection.
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Prep Time 30 minutes
Cook Time 1 hour 5 minutes
Total Time 1 hour 35 minutes
Servings: 8
Course: Side Dish
Cuisine: American
Calories: 450
Ingredients Equipment Method Notes

Ingredients
  

  • 3 lbs sweet potatoes, peeled and thinly sliced about 1/8 inch thick
  • 1 medium yellow onion, thinly sliced
  • 4 cloves garlic, minced
  • 1/4 cup unsalted butter
  • 1/4 cup all-purpose flour
  • 3 cups whole milk
  • 1 cup heavy cream
  • 1/2 teaspoon ground nutmeg
  • 1/4 teaspoon ground cinnamon
  • 1 teaspoon salt
  • 1/2 teaspoon black pepper
  • 1 cup shredded Gruyere cheese or Swiss cheese
  • 1/2 cup grated Parmesan cheese
  • 2 tablespoons chopped fresh sage optional

Equipment

  • 9x13-inch baking dish
  • Large saucepan
  • Mandoline or sharp knife
  • whisk
  • aluminum foil
  • Measuring cups
  • Measuring spoons

Method
 

  1. Preheat oven to 375°F (190°C). Grease a 9x13 inch baking dish.
  2. Thinly slice the sweet potatoes and onion using a mandoline or sharp knife. Ensure consistent thickness for even cooking.
  3. In a large saucepan, melt the butter over medium heat.
  4. Add the minced garlic and cook for about 30 seconds, until fragrant.
  5. Whisk in the flour and cook for 1-2 minutes, stirring constantly, to create a roux.
  6. Gradually whisk in the milk, ensuring there are no lumps. Bring to a simmer, stirring constantly.
  7. Reduce heat to low and simmer for 5-7 minutes, or until the sauce has thickened slightly.
  8. Stir in the heavy cream, nutmeg, cinnamon, salt, and pepper. Remove from heat.
  9. Arrange a layer of sweet potato slices in the prepared baking dish, overlapping slightly.
  10. Top with a layer of onion slices.
  11. Drizzle about 1/3 of the cream sauce over the sweet potatoes and onions.
  12. Sprinkle with 1/3 of the Gruyere and Parmesan cheeses, and 1/3 of the sage (if using).
  13. Repeat layers twice more, ending with a layer of cheese.
  14. Cover the baking dish with aluminum foil. Bake for 45 minutes.
  15. Remove the foil and bake for an additional 15-20 minutes, or until the sweet potatoes are tender and the cheese is golden brown and bubbly. A knife inserted into the sweet potatoes should meet little resistance.
  16. Let the casserole rest for 10-15 minutes before serving. This allows the sauce to thicken slightly and the flavors to meld.

Notes

For best results, ensure sweet potatoes are sliced uniformly to 1/8 inch thickness. Browning the butter before adding flour enhances the flavor. Resting the casserole after baking is crucial for the sauce to thicken. Store leftovers in the refrigerator for up to 3 days.