Scalloped Potatoes

The quickest way to slice the potatoes is in a food processor fitted with an ⅛-inch (~3mm) slicing blade. If the potatoes are too long to fit into the feed tube, halve them crosswise and put them in the feed tube cut-side down so that they sit on a flat surface.  Of course, you can slice the potatoes by hand.

2 tablespoons unsalted butter
1 medium onion, minced (about 1 cup)
1¼ teaspoons salt
¼ teaspoon pepper
2½ pounds russet potatoes (about 5 medium), peeled and sliced 1/8-inch thick 
2 cups milk
4 ounces grated cheddar cheese, shredded (1 cup)
Bread crumbs to top 

1.    Adjust oven rack to middle position; heat oven to 425°.

2.    Melt butter in large Dutch oven and add onion and cook, stirring occasionally, until soft and lightly browned, about 4 minutes.

3.    Add potatoes, milk, and salt and pepper, and bring to simmer.

4.    Cover, reduce heat to medium-low, and simmer until potatoes are almost tender (about 10 minutes.

5.    Transfer mixture to 8-inch-square baking dish (or other 1½-quart gratin dish)

6.    Sprinkle evenly with cheese and top with bread crumbs.

7.  Bake until milk is bubbling around edges and top is golden brown, about 15 minutes. Cool 10 minutes before serving.

To Make Ahead:

    Once the scalloped potatoes have been transferred to the baking dish and pressed into an even layer in step 2, they can be wrapped in plastic wrap and refrigerated for up to 24 hours. When ready to bake, add the cheese, cover with foil, and bake in a 400-degree oven until the mixture is hot and bubbling, about 45 minutes. Remove the foil and cook until the cheddar begins to brown, about 30 minutes longer. Let cool for 10 minutes before serving.