POTATO, CELERY ROOT AND LEEK GRATIN (for eight)

 

3 cups heavy cream

2 garlic cloves, peeled

1 sprig thyme plus 3 teaspoons fresh thyme leaves, divided

2 tablespoons (1/4 stick) unsalted butter, divided

3 leeks, white and pale green parts only, halved lengthwise, thinly sliced crosswise

kosher salt

2 pounds russet potatoes, peeled, very thinly sliced crosswise (1/8 inch)

1 pound celery root, peeled, very thinly sliced crosswise (1/8 inch)

2 cups grated Gruyere

freshly ground black pepper

 

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1. Preheat oven to 350*. Heat cream, garlic and thyme sprig in a medium saucepan just until bubbles begin to form around edge of pan. Remove from heat and set aside to steep.

2. Melt 1 tablespoon butter in a medium skillet over medium heat. Add leeks, season with salt and cook, stirring often, until tender (do not brown), 10 to 12 minutes. Transfer to a small bowl and set aside.

3. Butter a 3 quart gratin dish with remaining 1 tablespoon butter. Layer 1/3 of potatoes and 1/3 of celery root slices evenly over bottom of baking dish. Cover with 1/3 of leeks, then 1/3 of Gruyere. Sprinkle with salt, pepper and 1 teaspoon thyme leaves. Repeat layers twice more. Strain cream mixture into a medium pitcher and pour over vegetables.

4. Set gratin dish on a large rimmed baking sheet and cover tightly with foil. Bake for 1 hour. Carefully remove foil. Continue baking until top is golden brown and sauce is bubbling, 30 to 35 minutes, more if needed to cook the celery root completely through.

NOTE: Can be made 2 hours ahead. Let stand at room temperature. Tent with foil and rewarm in a 300* oven until hot, about 20 minutes.

 

from Bon Appetit magazine, November, 2011