Recipe: Cast-Iron Potato Gratin [with video]
This recipe is part of the Just Picked series, a partnership between Modern Farmer + Foodterra. Visit our recipe hub for the complete collection, which will be growing throughout the season.
Whether you call this gratin dauphinoise, like the French, or scalloped potatoes, as folks do in the Midwest, this luxuriously creamy potato casserole, topped with a golden brown crown of Gruyère and Comté, is comfort food at its best. If you want to make this dish even more decadent, sprinkle grated Parmesan evenly into the buttered pan before topping with the potatoes for an extra layer of goodness. Serve with a juicy steak and a bold red wine.
- Olive oil, as needed
- 4–5 tablespoons unsalted butter
- 2 leeks, green parts removed, white parts quartered lengthwise, soaked in water to remove dirt, and chopped into half moons
- ½ shallot, finely chopped
- 3–4 cloves garlic, minced
- Salt and freshly ground black pepper
- 3–4 cups whole milk
- ½ cup heavy cream (optional)
- 4–5 large baking potatoes, such as Russets (we used ‘Purple Vikings’), peeled and cut crosswise into ¼-inch-thick slices using a mandolin
- 2–3 teaspoons freshly grated nutmeg
- 1 cup grated Gruyère cheese, preferably cave aged
- 1 cup grated Comté cheese, preferably cave aged
- 1 small bunch chives, finely chopped
Preheat a heavy-bottomed enameled pot over medium to medium-high heat. Generously coat pot with oil, followed by 3–4 tablespoons butter. Stir until butter is melted and incorporated into oil (do not let butter brown).
Stir in leeks, shallots, and garlic and season with salt and pepper. Gently sauté for 5–6 minutes until softened. Reduce heat to medium and pour in 2 cups milk and heavy cream (if using). Stir in potato slices and season generously with salt, pepper, and nutmeg. Potatoes should protrude just above milk; if they don’t, add more milk accordingly. Simmer, stirring frequently with a wooden spoon and checking seasoning occasionally, until milk mixture thickens, 15–20 minutes.
Meanwhile, preheat oven to 400–425°F. Grease bottom and sides of a medium cast-iron skillet with remaining 1 tablespoon butter.
Check reduced milk mixture for thickness by moving wooden spoon along bottom of pot to expose the surface; if barely any liquid fills the void, add a little more milk. Continue to cook, stirring occasionally, just until potato slices break when folded in half with your fingers, about 10 minutes. (Be careful not to overcook potatoes.)
Turn off heat and spoon potato mixture into prepared cast-iron skillet, patting potato slices down as you go to fill pan completely. Cover the top evenly with Gruyère and Comté and bake in oven until gratin is bubbly and cheeses are browned and crispy, 15–20 minutes.
Remove from oven and immediately top with chives so they cook a bit in the hot oil and cheeses. Let cool slightly before serving.