Potato gratin is a notoriously heavy side dish, laden with cream and gooey cheese. We wanted to shift the focus of this classic side dish to the potatoes.
We chose Yukon Gold potatoes for their rich flavour and moderate starch content, which helped them hold their shape when cooked. Tossing the potatoes with fruity, flavourful extra-virgin olive oil heightened the flavour of the potatoes but didn’t overpower them.
For a crisp, cheesy topping, we mixed more olive oil with panko bread crumbs and sprinkled the dish with sharp, salty Pecorino-Romano. For added depth, we added sauteed onions, fresh thyme, and garlic.
OLIVE OIL POTATO GRATIN
Start to finish: 2 hours
2 ounces Pecorino-Romano cheese, grated (1 cup)
1/2 cup extra-virgin olive oil
1/4 cup panko bread crumbs
Salt and pepper
2 onions, halved and sliced thin
2 garlic cloves, minced
1 teaspoon minced fresh thyme
1 cup low-sodium chicken broth
3 pounds Yukon Gold potatoes, peeled and sliced 1/8 inch thick, preferably with a mandoline
Adjust oven rack to upper-middle position and heat oven to 400 F. Grease 13-by-9-inch baking dish. Combine Pecorino, 3 tablespoons oil, panko, and 1/2 teaspoon pepper in bowl; set aside.
Heat 2 tablespoons oil in 12-inch skillet over medium heat until shimmering. Add onions, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring frequently, until browned, about 15 minutes. Add garlic and 1/2 teaspoon thyme and cook until fragrant, about 30 seconds. Add 1/4 cup broth and cook until nearly evaporated, scraping up any browned bits, about 2 minutes. Remove from heat; set aside.
Toss potatoes, remaining 3 tablespoons oil, 1 teaspoon salt, 1/2 teaspoon pepper, and remaining 1/2 teaspoon thyme together in bowl. Arrange half of potatoes in prepared dish, spread onion mixture in even layer over potatoes, and distribute remaining potatoes over onions. Pour remaining 3/4 cup broth over potatoes. Cover dish tightly with aluminum foil and bake for 1 hour.
Remove foil, top gratin with reserved Pecorino mixture, and continue to bake until top is golden brown and potatoes are completely tender, 15 to 20 minutes. Let cool for 15 minutes. Serve.