ROOT VEGETABLE GRATIN

WHY THIS RECIPE WORKS:

Sweet rutabaga and herbal celery root complement the earthiness of potatoes in our root vegetable gratin. We allowed all these flavors to come to the forefront by adding just a few aromatics: onion, garlic, thyme, and Dijon mustard. We added white wine to the gratin mixture because the wine’s acidity strengthens the pectin in the potatoes, ensuring they remain intact while the denser, less-starchy rutabaga and celery root cook through; the wine also brightens the flavor of the vegetables. To help the top layers of the gratin cook through at the same rate as the bottom layers, we covered the dish for the first portion of the cooking time. A layer of Parmesan-enhanced panko bread crumbs, added after removing the foil, toasted to a golden brown while the gratin finished cooking, resulting in a crispy, nutty, cheesy crust. Uniform thin slices of rutabaga, celery root, and potatoes are key to even cooking—use a mandoline, a V-slicer, or the slicing disk on a food processor.

SERVES: 6 to 8

TOTAL TIME: 1 hour 45 minutes (plus 25 minutes resting time)

INGREDIENTS:

• 1 tablespoon plus 1½ cups water
• 2 teaspoons all-purpose flour
• 1½ teaspoons Dijon mustard
• Salt and pepper
• ⅔ cup dry white wine
• ½ cup heavy cream
• ½ onion, chopped fine
• 1¼ teaspoons minced fresh thyme
• 1 garlic clove, minced
• 2 pounds large Yukon Gold potatoes, peeled and sliced ⅛ inch thick
• 1 pound rutabaga, trimmed, peeled, quartered, and sliced ⅛ inch thick
• 1 pound celery root, trimmed, peeled, quartered, and sliced ⅛ inch thick
• ¾ cup panko bread crumbs
• 1½ ounces Parmesan cheese, grated (¾ cup)
• 4 tablespoons unsalted butter, melted and cooled

INSTRUCTIONS:

1. PREPARE THE DISH:

• Adjust oven rack to middle position and preheat oven to 375 degrees.
• Grease a 13 by 9-inch baking dish.

2. MAKE THE GRATIN:

• Whisk 1 tablespoon water, flour, mustard, and 1½ teaspoons salt in a bowl until smooth.
• Add wine, cream, and remaining 1½ cups water, whisking to combine.
• Combine onion, thyme, garlic, and ¼ teaspoon pepper in a separate bowl.
• Layer half of potatoes in prepared dish, arranging so they form an even thickness.
• Sprinkle half of onion mixture evenly over potatoes.
• Arrange rutabaga and celery root slices in an even layer over onions.
• Sprinkle remaining onion mixture over rutabaga and celery root.
• Layer remaining potatoes over onions.
• Slowly pour water mixture over vegetables.
• Using a rubber spatula, gently press down on vegetables to create an even, compact layer.
• Cover tightly with aluminum foil and bake for 50 minutes.
• Remove foil and continue to bake until a knife inserted into center of gratin meets no resistance, 20 to 25 minutes.

3. MAKE THE TOPPING AND FINISH THE GRATIN:

• Meanwhile, combine panko, Parmesan, and butter in a bowl and season with salt and pepper.
• Remove gratin from oven and sprinkle evenly with panko mixture.
• Continue to bake until panko is golden brown, 15 to 20 minutes.
• Remove gratin from oven and let sit for 25 minutes.
• Serve