Ingredients
10 tablespoons unsalted butter
4 cups thinly sliced onions
2 1/2 teaspoons coarse salt
1 1/4 teaspoons freshly ground black pepper
5 pounds red bliss potatoes, peeled and sliced into 1/8-inch rounds
1 tablespoon finely chopped fresh thyme
1 1/2 cups low-sodium store-bought chicken stock or broth
Preparation
Preheat oven to 400 degrees.
Melt 2 tablespoons butter in a large skillet over medium heat. Add onions and cook, stirring frequently, until caramelized, about 30 minutes. Season with 1/2 teaspoon salt and 1/4 teaspoon black pepper. Transfer onions to a large bowl and let cool.
In the same skillet, melt 2 tablespoons butter over medium-high heat, and cook a quarter of the potatoes until lightly caramelized, about 5 minutes. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Transfer to a platter and let cool. Repeat process three more times with remaining butter, potatoes, salt, and pepper.
Arrange a quarter of the cooled potatoes in a slightly overlapping single layer in a 9-by-13-inch baking dish. Top with a third of the onions and sprinkle 1 teaspoon thyme over the dish. Layer another quarter of the potatoes over onions and thyme and top with another third of the onions and 1 teaspoon of thyme. Repeat process and finish with a layer of potatoes.
Pour chicken stock over potatoes and transfer baking dish to oven. Bake for 25 minutes; reduce oven temperature to 350 degrees, and continue baking until potatoes are golden brown, about 30 minutes more. Remove from oven and let cool 10 minutes before serving.
