Adjust oven rack to middle position; heat oven to 425 degrees.

Peel 2½ pounds russet potatoes and then slice ⅛-inch thick.

Melt 2 tablespoons unsalted butter in large Dutch oven over medium-high heat until foaming subsides.

Add 1 minced onion and cook, stirring occasionally, until soft and lightly browned, about 4 minutes.

Add 2 minced garlic cloves, 1 tablespoon chopped fresh thyme, 1¼ teaspoons table salt, and ¼ teaspoon pepper and cook until fragrant, about 30 seconds.

Add potatoes, 1 cup chicken broth, 1 cup heavy cream, and 2 bay leaves and bring to simmer.

Cover, reduce heat to medium-low, and simmer until potatoes are almost tender (paring knife can be slipped into and out of potato slice with some resistance), about 10 minutes.

Discard bay leaves.

Transfer mixture to 8-inch-square baking dish and press to an even layer; sprinkle evenly with 1 cup shredded cheddar cheese.

Bake until cream 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 3, 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.