The potatoes are perfectly tender in this easy Gruyère potato casserole. The cheese gets brown and crispy on the top and sides and the herbs add a nice accent to this savory dish.
Preheat oven to 400°F. Coat a 9-by-13-inch casserole dish with cooking spray.
Toss potatoes, shallots, oil, thyme, rosemary, pepper, salt, 3/4 cup Gruyère and 1/3 cup Parmesan together in a large bowl. Arrange in a decorative layer in the prepared dish. Pour broth evenly over the potato mixture. Sprinkle the top evenly with the remaining Gruyère and Parmesan. Cover tightly with foil.
Bake until the potatoes are tender and bubbly, about 40 minutes. Uncover and continue to bake until the cheese is browned, about 15 minutes more. Let stand for 10 minutes before serving. Sprinkle with thyme and rosemary before serving, if desired.