Grease a 9×13-inch baking dish with 2 tablespoons of butter or spray with cooking spray. Set aside.
Prepare the potatoes:
Peel and thinly slice the potatoes into about ⅛-inch thick slices. You can use a mandolin slicer for uniform slices.
Place the potato slices in a large bowl of cold water as you slice them to prevent browning. Drain and pat dry with a clean kitchen towel or paper towels before layering in the dish.
Make the creamy sauce:
In a large saucepan, melt 2 tablespoons of butter over medium heat.
Add the chopped onion and cook for about 4-5 minutes until soft and translucent.
Add the garlic and cook for another 30 seconds, until fragrant.
Pour in the heavy cream and milk. Stir well and bring to a simmer. Reduce the heat and let the mixture cook for about 3-4 minutes.
Stir in 1 teaspoon salt, ½ teaspoon black pepper, and thyme (if using). Taste the sauce and adjust seasoning if needed.
Layer the potatoes:
Arrange half of the potato slices in the bottom of the prepared baking dish, overlapping slightly.
Pour half of the creamy sauce over the first layer of potatoes.
Sprinkle with ½ cup of cheddar cheese and ½ cup of Gruyère cheese.
Add the second layer of potatoes on top, overlapping the slices again.
Pour the remaining sauce over the potatoes and top with the remaining cheese.
Bake:
Cover the baking dish tightly with aluminum foil.
Bake for 45 minutes. Then, remove the foil and continue baking for another 30-35 minutes until the potatoes are tender and the top is golden brown and bubbly. If the top isn’t as golden as you’d like, you can broil it for a couple of minutes to achieve a crisp, golden crust.
Garnish and serve:
Remove from the oven and let it sit for 5-10 minutes before serving. This helps the sauce to thicken and makes it easier to slice.
Garnish with freshly chopped parsley if desired for a pop of color.
Ingredients
2 lbs russet potatoes (about 4 large potatoes), peeled and thinly sliced
2 tbsp unsalted butter (for greasing the dish)
2 tbsp unsalted butter (for the sauce)
1 small onion, finely chopped
2 cloves garlic, minced
2 cups heavy cream (you can substitute half-and-half for a lighter version)
1 cup milk
1 ½ tsp salt (divided)
½ tsp black pepper
1 tsp fresh thyme (optional, or ½ tsp dried thyme)
1 ½ cups shredded sharp cheddar cheese
1 ½ cups shredded Gruyère cheese (or mozzarella for a milder cheese)
1 tbsp fresh parsley (for garnish, optional)
Tips
Make-Ahead: You can assemble the dish the day before and refrigerate it overnight. Just cover it tightly with foil and bake it the next day as directed, adding a little extra baking time if needed.
For extra richness: You can replace part of the milk with more heavy cream, or add a bit of cream cheese to the sauce.
Cheese Variations: Feel free to experiment with different cheeses! Fontina, Monterey Jack, or even a bit of Parmesan can be great alternatives or additions.
Crispier top: For an even crunchier topping, sprinkle panko breadcrumbs or additional shredded cheese on top before the final bake, and broil for a minute or two to get that crispy, golden finish.
Enjoy your creamy, cheesy scalloped potatoes—perfect for any family dinner or holiday feast!