Lightened-Up Scalloped Potato Gratin

This Lightened-Up Scalloped Potato Gratin is everything you want in a cozy side dish: tender layers of Yukon Gold potatoes, a creamy and flavorful sauce, and a golden cheesy topping. Unlike traditional versions, this recipe keeps things lighter without sacrificing the rich and comforting taste. It is perfect for holidays, weeknight dinners, or potlucks and pairs beautifully with chicken, beef, seafood, or vegetarian mains.

Ingredients

For the Potatoes:

900 g Yukon Gold potatoes (about 5–6 medium), peeled and thinly sliced
1 small onion, finely minced (optional but recommended for flavor)
Salt and black pepper to taste

For the Lightened Sauce:

2 tablespoons butter
2 tablespoons olive oil
3 tablespoons all-purpose flour
2 cups low-fat milk (2% works best)
1/3 cup low-sodium chicken broth or vegetable broth
1 teaspoon garlic powder
1 teaspoon onion powder
1/2 teaspoon paprika
1 teaspoon Dijon mustard (optional but enhances flavor)
1 teaspoon fresh thyme or 1/2 teaspoon dried thyme

Cheese Topping:

1 cup shredded sharp cheddar cheese
1/3 cup grated Parmesan cheese

Instructions

Prepare the Potatoes
Preheat your oven to 190°C (375°F). Grease a medium baking dish (approximately 9×13 inches) with butter or olive oil. Peel the potatoes and slice them into thin, even rounds, about 3–4 mm thick. A mandoline slicer works best for consistent thickness.
Make the Lightened Cream Sauce
In a medium saucepan, melt the butter with olive oil over medium heat. Whisk in the flour and cook for 1 minute until slightly golden and fragrant. Slowly pour in the milk while whisking continuously to avoid lumps. Add the broth and continue whisking until the mixture thickens.

Stir in garlic powder, onion powder, Dijon mustard, paprika, thyme, salt, and pepper. Taste and adjust seasoning as needed.
Assemble the Gratin
Layer one-third of the sliced potatoes in the baking dish. Season lightly with salt and pepper. Pour one-third of the cream sauce over the potatoes and sprinkle with a little cheddar and Parmesan. Repeat the layers two more times, finishing with the remaining cheeses on top.
Bake
Cover the dish with foil and bake for 40 minutes. Remove the foil and bake for an additional 20–25 minutes, or until the top is golden brown and the potatoes are tender when pierced with a knife.
Rest and Serve
Let the gratin rest for 10 minutes before serving. This helps the sauce set and makes slicing easier.

Tips for Best Results

Use Yukon Gold potatoes for the best texture and naturally buttery flavor.
Shred cheese from a block instead of using pre-shredded cheese; it melts more smoothly.
If the top browns too quickly during baking, loosely tent with foil.

Storage and Reheating

Refrigerate: Store leftovers in an airtight container for up to 4 days.
Reheat: Warm in the oven at 160°C (325°F) for 10–15 minutes or until heated through.
Freezing: Not recommended, as potatoes may become grainy after thawing.

Serving Ideas

This Lightened-Up Scalloped Potato Gratin pairs well with baked chicken, roast beef, grilled fish, or a fresh salad for a balanced meal. It also makes an excellent side dish for holiday dinners and special occasions.