Olive Oil Potato Gratin

"Why this recipe works:Most gratins are loaded down with cream and gooey cheese, but for a potato gratin that actually tasted like potatoes, we skipped the dairy case. We chose fruity, flavorful extra-virgin olive oil to add richness to earthy Yukon Gold potatoes. Some of the oil gets tossed with the spuds before they go in the casserole dish, and some is used to sauté onions and thyme until they’re deep golden. We layer the onions with the potatoes, moisten them with savory chicken broth, cover the dish, and bake it until everything is nearly tender. Then we finish it off with a golden-brown topping of Parmesan cheese, crisp panko bread crumbs, and even more extra-virgin olive oil...."