Baking Gratin In This Pan Makes The Crispest Golden Crust With No Extra Work

Whether you know it as au gratin or Daphinoise, few things beat the delicious comfort of a side dish of thinly sliced potatoes, baked slowly in a creamy sauce, topped with a crispy, golden crust. While this simple dish requires just a handful of basic ingredients, there are some important tips you need when making au gratin potatoes to elevate the humble side to new heights. And if you're a fan of the cheesy top and crunchy bits around the edges, we have another helpful tip for you: forego the casserole dish and make your potatoes au gratin in a sheet pan. 

Baking potatoes au gratin in a sheet pan exposes more surface area to direct oven heat, maximizing browning and creating a higher crust-to-cream ratio. However, this doesn't mean you'll have to sacrifice a creamy, soft middle. With this method, you will get the best of both worlds—a wonderfully creamy center surrounded by a fabulous cheesy potato crust. 

Now, you might think potatoes au gratin are the same as scalloped potatoes, but there is a crucial difference between the two that concerns the sheet pan cooking method. While they both include potatoes and cream, scalloped potatoes do not contain cheese, so you won't get the same cheesy, crispy layer that distinguishes potatoes au gratin. The top of the scalloped potatoes will brown, but it won't be as crispy as that of a potato gratin.

Before you get started, make sure that you use a potato that will hold its shape in the cooking process. There are many kinds of potatoes out there, but using Yukon Gold potatoes will give you better results. Yukons are creamier, less starchy, more flavorful, and they hold their shape well as they are denser than russets and absorb less moisture. Of course, if you prefer red or russet potatoes, they will work, too.

A classic potatoes au gratin recipe calls for Gruyère cheese, but don't let that limit you. You can use any flavorful cheese that melts well, such as cheddar or Gouda. A blend of cheeses will add extra flavor and a different texture, so feel free to experiment with your favorites—some recipes even include Parmesan or Pecorino Romano for even more depth of cheesey flavor. 

For crispiest results, use a mandolin slicer to cut the potatoes. A mandolin will let you choose the thickness of the slices while keeping them uniform, which will help them cook evenly. Aim for an ideal width between ⅛ and ¼ inch.

Use a sheet pan with a lip so it holds the creamy sauce without spilling over. Make sure you grease the sheet pan extremely well, using cooking spray, oil, or butter, to make sure the potatoes don't stick. Alternately, line it up with well-oiled aluminium foil for easier clean-up. Cover the potatoes with aluminium foil and bake at 450 degrees Fahrenheit for 20 minutes. Remove the foil and bake for another 20-25 minutes until the top is golden and crispy.