Sheet Pan Scalloped Potatoes

The best part of scalloped potatoes is arguably the golden top layer with its crackling edges and crispy brown bits. It gives a perfect umami contrast to the creamy, tender potatoes underneath. So why not just make the whole thing like that? Turns out, you can (and should!). And it's as simple as swapping out your baking dish for a sheet pan. A greater surface area with fewer layers means more of that magically browned and bubbling crust. Grab your humble sheet pan and give this method a go you'll wonder why you didn't try it sooner.

Why Use a Sheet Pan to Make Scalloped Potatoes?

Scalloped potatoes are typically piled high in a casserole dish and baked with milk or cream until tender sometimes spending up to an hour or more in the oven. Using an 18x13-inch sheet pan in place of a 9x13-inch baking dish streamlines the process by spreading the potatoes out into a thin layer, ensuring they cook to tender perfection while maintaining a delightful crispiness on top. And with two layers of thinly sliced potatoes, rather than the classic three-plus, the cooking and prep times are shortened overall. But don't worry, you also still get that gooey, molten potato layer below the surface as well using this sheet pan trick.

How to Make Sheet Pan Scalloped Potatoes

To really take it to the next level, this recipe doubles down on flavor by adding caramelized onions and cheese. Technically this makes it more of an au gratin because of the Parmesan and Cheddar, but "potato, potahto," right? It has the heart of a scalloped potato with its signature shingled look and rich creamy depth. Add these items to your grocery list and follow the steps to get cooking.

Ingredients:

• 3 tbsp unsalted butter, softened, divided
• 5 cups thinly sliced yellow onions (1 1/4 lbs total onions)
• 2 cups heavy whipping cream
• 2 tbsp thinly sliced garlic (2 large cloves)
• 1 1/2 tsp fresh thyme leaves, plus more for garnish
• 1/2 tsp chopped fresh rosemary
• 1/4 tsp black pepper
• 2 1/2 tsp kosher salt, divided
• 2 1/2 lbs medium Yukon Gold potatoes, scrubbed (about 8)
• 1 1/2 oz Parmesan, finely shredded, divided (about 2/3 cup)
• 6 oz extra-sharp white Cheddar cheese, shredded (about 1 1/2 cups)

Step-By-Step Guide:

1. Preheat the oven to 450F (230C). Grease the bottom and sides of an 18x13-inch sheet pan with 1 tbsp of butter.
2. Melt the remaining 2 tbsp of butter in a large nonstick skillet over medium heat. Add the onions and cook, covered, stirring occasionally, for 5-7 minutes until soft and translucent.
3. Reduce the heat to medium-low and continue cooking, uncovered, stirring occasionally, for 30-35 minutes until the onions are soft and brown. Remove from heat.
4. While the onions are cooking, bring the cream, garlic, thyme, rosemary, pepper, and 1/2 tsp salt to a simmer in a small saucepan over medium heat. Remove from heat immediately.
5. Thinly slice the potatoes using a mandoline into 1/8-inch-thick rounds. If you don't have a mandoline, carefully slice the potatoes as evenly as possible with a sharp knife.
6. Arrange half of the potato slices (about 3 1/2 cups) in a single, overlapping layer on the prepared sheet pan, making sure no bottom of the sheet is visible.
7. Sprinkle the first layer evenly with 1 tsp salt, caramelized onions, and 1/3 cup Parmesan.
8. Top with the remaining potato slices in a single overlapping layer. Sprinkle with the remaining 1 tsp salt.
9. Pour the hot cream mixture evenly over the potatoes. Cover the sheet pan tightly with foil.
10. Bake in the preheated oven for 20-25 minutes until the potatoes are tender when pierced with a fork.
11. Carefully remove the foil and scrape off any potato or garlic slices that may be sticking to it. Sprinkle the Cheddar cheese and remaining 1/3 cup Parmesan on top.
12. Return the pan to the oven, uncovered, and bake for another 15-20 minutes, rotating the pan halfway through, until the top is golden and crusty.
13. Sprinkle with more thyme leaves and serve immediately.

Recipe Tips:

• If you dont have a mandoline guard, use a clean kitchen towel as a buffer between your hands and the mandoline blade.
• If your onions start to get unevenly browned, add a splash (1-2 tbsp) of water to the skillet to help them cook more evenly.

How to Serve Sheet Pan Scalloped Potatoes:

Sheet pan scalloped potatoes can be served directly from the oven, garnished with fresh thyme or your favorite herb. These make a perfect side dish for grilled or roasted meats such as steak, chicken, pork, or especially ham. They also pair wonderfully with fish like pan-roasted salmon. Alternatively, they are delicious enough to stand on their own as a main dish!

Substitutions and Variations:

Feel free to customize the recipe based on your preferences:

• Swap the cheese: Try Gruyre or Comt instead of extra-sharp Cheddar and Grana Padano or Pecorino Romano instead of Parmesan for different flavor profiles.
• Replace the onions: Sweet onions caramelize faster, or you could add fennel during cooking for a unique twist. If you're not a fan of caramelized onions, you can skip them entirely.
• Substitute the potatoes: Russets or sweet potatoes can be used, though they may require slightly adjusted cooking times. Ensure they are starchy for the best results.

How to Make Sheet-Pan Scalloped Potatoes Ahead of Time:

While slicing potatoes ahead of time is not recommended (they can oxidize and turn brown), there are other steps you can prepare in advance. Caramelized onions can be made ahead and stored in the fridge for up to a week. You can also shred the cheeses in advance and store them in an airtight for up to a week.

How to Store Sheet Pan Scalloped Potatoes:

Leftovers can be kept in an airtight in the fridge for 3-4 days. To reheat, simply pop them back in the oven or microwave. Freezing is not recommended for this dish as the cream and cheese may separate when thawed. However, theres a good chance you wont have leftovers to freeze!