Steps

• 1

  When ready to cook, set Traeger to 400°F and preheat, lid closed for 15 minutes.

  400 ˚F / 204 ˚C

  00:15

• 2

  Butter a 9x13 baking dish with 1 tablespoon of the softened butter. In a medium frying pan over medium heat, melt the remaining butter. Add the leeks and a generous pinch of salt and pepper and cook, stirring often until softened, about 5 minutes.

  00:05

• 3

  Remove from the heat and allow to cool. Place the potato and celery root slices into a large mixing bowl. Add the cream, leek mixture, minced sage, 1 teaspoon salt, 1/2 teaspoon pepper and 1 cup cheese. Stir gently to coat.

• 4

  Arrange a layer of potato and celery root slices so they’re slightly overlapping in the prepared baking dish. Repeat two more times so there are three layers of potatoes. Pour remaining cream from the bowl over the gratin, then sprinkle the top with the remaining cup of cheese.

• 5

  Cover the dish loosely with foil and bake on the grill for 45 minutes. Remove the foil and continue baking until the top is golden and bubbly and the potatoes are tender when pierced, about 30 to 45 minutes longer. Let stand for 10 minutes before serving. Enjoy!

  01:15