Ingredients
Equipment
Method
Prep and preheat
- Preheat oven to 375F, then butter a 9x13-inch baking dish with butter so the potatoes won’t stick.
- Peel and slice the russet potatoes into 1/8 inch-thick rounds, and thinly slice the onion for even layering.
Make the creamy sauce
- Melt 4 tablespoons butter in a Dutch oven, add minced garlic, and cook for 30 seconds until fragrant.
- Whisk in all-purpose flour and cook for 1 minute to remove the raw flour taste.
- Gradually whisk in the whole milk and heavy cream, then simmer until slightly thickened.
- Season the sauce with salt, black pepper, and fresh thyme leaves, stirring until evenly combined and glossy.
Assemble and bake
- Layer half of the sliced potatoes and onion in the baking dish, then pour sauce over the layer to coat.
- Add a second layer of potatoes and onion, pour sauce over it, then finish with a third layer and pour remaining sauce over the top.
- Cover the dish with foil and bake for 1 hour to cook through the potato layers.
- Uncover, sprinkle with grated Parmesan, and bake 25-30 minutes at 375F until golden on top and fork-tender.
Rest and serve
- Rest the scalloped potatoes for 15 minutes before serving so the sauce thickens slightly and layers hold together.
Notes
Pro tip: Slice the potatoes consistently (about 1/8 inch) so they cook at the same rate and create tender, even layers. Refrigerate leftovers in a sealed container for up to 3-4 days; reheat covered in a 350F oven until warmed through. Freezing is not recommended due to texture changes in the dairy sauce. For a lighter option, replace half of the heavy cream with more whole milk while keeping the Parmesan for structure and flavor.