Ingredients

The following ingredients have 8 Servings
  • 4 (about 2 pounds) russet potatoes (peeled and cut into 1-inch (25-mm) pieces)
  • 3 1/2 teaspoons Diamond Crystal kosher salt (or 2 teaspoons Morton kosher salt)
  • 2 1/4 cups half-and-half
  • 1 1/2 sticks (6 oz) unsalted butter
  • 1/2 teaspoon ground white pepper
  • 1/4 teaspoon freshly grated nutmeg
  • 1 large egg yolk
  • 1/2 cup panko bread crumbs
  • 1/4 cup freshly grated Parmesan cheese
  • 1 tablespoon chopped fresh parsley
  • 1 tablespoon extra-virgin olive oil

Instruction

  • Preheat the oven to 350°F (177C).
  • Place potatoes in a large pot and add 2 teaspoons salt (1 teaspoon, if using Morton) and enough cold water to cover by 2 inches (5 cm). Bring the potatoes to a boil over high heat, then reduce heat and simmer until tender, 10 to 20 minutes.
  • Drain the potatoes and return to the hot pot. Place over low heat and simmer until dry, then use a potato masher to thoroughly mash the potatoes.
  • In a small saucepan over medium heat, warm the half-and-half, butter, pepper, and nutmeg until the butter melts. Remove from the heat.
  • Place the egg yolk in a small bowl. Ladle in a small scoop of the warm milk mixture and whisk to temper the yolk. Whisk the tempered egg yolk back into the milk mixture.
  • Slowly whisk the milk mixture into the potatoes. The potato mixture will be very loose. Season with the remaining 1 1/2 teaspoons salt (1 teaspoon, if using Morton).
  • Butter an 8x12-inch (20-by 30-cm) oval gratin baking dish.
  • In a small bowl, combine panko, parmesan, parsley, and oil. Pour the mashed potatoes into the dish. Sprinkle with the breadcrumb mixture. (Can be made 6 hours ahead. Cover and refrigerate.)
  • Bake gratin until the top is golden brown and heated through, 35 to 45 minutes. If made ahead, allow for an extra 10 minutes of cooking time.☞TESTER TIP: If your gratin seems a little loose after baking, let it cool for a few minutes. It should firm right up.