I learned a trick from a chef in culinary school that never fails to make a well-seasoned, perfectly cooked, and beautifully golden gratin. Potato gratins are often baked entirely in the oven, but by first simmering the sliced potatoes on the stovetop in milk and cream, the starch is activated and this jump-starts the cooking process, ensuring an evenly baked gratin and offering you the opportunity to adjust the seasoning before it goes in the oven. I love to use any good-flavored cheese and urge you to use a high-quality Gruyère, Tomme de Savoie, or Comté. Because potatoes take on the flavors in the dish you are making, the cheese’s unique flavor will come through. Leeks are a natural with potato, and the nutmeg adds just a hint of warmth. A potato gratin is fit for a crowd, as it can be made ahead and is impressive looking. If it’s just for a family supper, leftovers are always relished. It’s not possible to make too much.
Because the texture and starchiness of the potato are key to the gratin’s success, use russets.
If making the gratin ahead, be aware that potatoes will soak up any residual liquid (the same holds for mashed potatoes). To make ahead, use 1/2 cup more liquid than when you serve it straight out of the oven.
High quality cheese and russet potatoes make this gratin golden, perfectly cooked, and completely leftover-worthy--if there is any left over.
- Preheat the oven to 350°F/180°C. Prepare a 3-qt gratin dish by rubbing the inside surface first with the cut garlic and then coating with the butter.
- Melt the butter in a large pot over medium heat. Add the leek or onion and cook, stirring often, until tender but not yet browned, about 3 minutes.
- Add the potatoes, milk, cream, garlic, nutmeg, and salt to the pot with the cooked leek or onion and bring to a boil over medium-high heat. Once at a boil, decrease the heat to medium and simmer for 5 minutes, stirring continuously. The starch in the potatoes will begin to thicken the milk and cream. Turn off the heat and stir in the cheese. Transfer the potato mixture to the gratin dish. Level the surface. Taste the liquid and season with more salt, if necessary (depending on the saltiness of the cheese).
- Scatter the cheese evenly over the top of the gratin. (The unbaked, assembled gratin can be covered and refrigerated for up to 2 days or tightly wrapped and frozen for up to 3 months.)
- Bake for 45 minutes to 1 hour, until the cheese on top is nicely browned and bubbling. If baking the gratin from the refrigerator or freezer, let it come to room temperature first and then bake. Let cool slightly before serving.
Reprinted with permission from Tartine All Day: Modern Recipes for the Home Cook by Elisabeth Prueitt, copyright © 2017. Published by Lorena Jones Books/Ten Speed Press, an imprint of Penguin Random House LLC.