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Potato Gratin Recipe

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★★★★★

4.9 from 72 reviews

A creamy and flavorful Potato Gratin made with thinly sliced sweet potatoes baked in a rich, cheesy sauce infused with garlic, fresh herbs, and warm spices. This comforting dish layers smoked gouda, Colby Jack, and asiago cheeses with a creamy herb sauce, perfect as a hearty side or vegetarian main.

Ingredients

Scale

Potatoes

  • 3 lbs sweet potatoes, peeled, rinsed, and thinly sliced into 1/8” rounds (mandoline slicer preferred)

Sauce

  • 4 tbsp butter
  • 2 cloves garlic, minced or pressed
  • 1 small red onion, finely diced
  • 1 tbsp all-purpose flour
  • 1 cup heavy cream
  • 1 cup half and half or whole milk
  • 1/2 tbsp finely chopped fresh rosemary leaves
  • 1 tsp smoked paprika
  • 1/4 tsp ground sage
  • 1/2 tsp Diamond Kosher salt
  • 1/4 tsp freshly ground black pepper
  • 1/4 tsp freshly grated nutmeg

Cheese

  • 1/3 cup grated asiago cheese
  • 1 cup smoked gouda cheese, shredded (divided)
  • 1 cup Colby Jack cheese, shredded (divided)

Instructions

  1. Preheat Oven: Preheat your oven to 400°F (204°C) to prepare for baking the gratin.
  2. Cook Aromatics: Melt butter in a large saucepan over medium heat. Add minced garlic and diced red onion, cooking and stirring occasionally until softened, about 5 minutes.
  3. Make Roux: Stir in the all-purpose flour and cook for 1 minute, stirring occasionally to avoid lumps.
  4. Add Dairy: Slowly whisk in the heavy cream and half and half (or whole milk) until well combined.
  5. Thicken Sauce: Increase heat to medium-high and cook for 3-4 minutes, stirring occasionally, until the sauce slightly thickens and begins to bubble. Remove from heat immediately.
  6. Season Sauce: Stir in grated asiago cheese, chopped fresh rosemary, smoked paprika, ground sage, kosher salt, black pepper, and freshly grated nutmeg. Let the sauce cool to room temperature to prevent cheeses from melting prematurely.
  7. Prepare Potatoes: While sauce cools, peel and thinly slice sweet potatoes using a mandoline or sharp knife (aim for 1/8” thickness).
  8. Arrange Potatoes: Grease a baking dish with butter or cooking spray. Arrange potato slices in a circular overlapping pattern. If not layering, toss potato slices with sauce and proceed to the next step.
  9. Combine Cheese and Sauce: Once cooled, stir half of the Colby Jack and half of the smoked gouda cheeses into the sauce. Note that the cheese will not melt at this stage.
  10. Assemble Dish: Pour the sauce evenly over arranged potatoes in the casserole dish. Top with the remaining shredded Colby Jack and smoked gouda cheeses.
  11. Bake Covered: Cover the dish tightly with foil and bake in the preheated oven for 45 to 50 minutes, or until potatoes are tender and can be easily pierced with a knife.
  12. Bake Uncovered: Remove the foil and continue baking for another 15 to 20 minutes until the top turns golden brown and bubbly.
  13. Rest and Serve: Let the gratin rest for 10 to 15 minutes before serving warm. For extra browning, optionally broil briefly while watching carefully to avoid burning, if your dish is broiler-safe.

Notes

  • Use a mandoline slicer to ensure evenly thin potato slices for uniform cooking.
  • If layering potatoes flat instead of circularly, mix them thoroughly with the sauce before placing in the baking dish.
  • Allowing the sauce to cool before combining with cheese prevents premature melting and ensures even distribution.
  • Substitute half and half with whole milk for a lighter sauce if desired.
  • For a crisper top, broil briefly at the end but watch closely to prevent burning.
  • This dish can be prepared ahead and baked just before serving.
  • Leftovers refrigerate well and can be reheated gently in the oven.

Keywords: Potato Gratin, Sweet Potato Gratin, Cheesy Potato Casserole, Holiday Side Dish, Creamy Potatoes, Baked Sweet Potatoes, Vegetarian Potato Dish

Find it online: https://cookwithlea.com/potato-gratin-recipe/