Name: Potato & Celery Root Gratin with Leeks
Yield: Makes 8 to 10 servings
Ingredients: 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" thick); 1 pound celery root, peeled, very thinly sliced crosswise (1/8" thick); 2 cups grated Gruyère; Freshly ground black pepper

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Potato & Celery Root Gratin with LeeksChristopher Testani

Celery root, also known as celeriac, has a knobby exterior that is best peeled (carefully!) with a paring knife.

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