Potato & Celery Root Gratin with Leeks

Ingredients

• 10 servings pepper black freshly ground
• 1 pound celery root thick peeled very thinly sliced ()
• 2  garlic clove peeled
• 2 cups gruyere cheese grated
• 3 cups cup heavy whipping cream 
• 10 servings kosher salt 
• 3  leek white halved lengthwise thinly sliced
• 2 pounds baking potatoes thick peeled very thinly sliced ()
• 1 sprig thyme leaves fresh divided
• 2 tablespoons butter unsalted divided ()

Equipment

• bowl
• sauce pan
• oven
• aluminum foil

Directions

1. Preheat oven to 350°F.
2. Heat cream, garlic,and thyme sprig in a medium saucepan justuntil bubbles begin to form around edge ofpan.
3. Remove from heat; set aside to steep.
4. Melt 1 tablespoon butter in a medium skilletover medium heat.
5. Add leeks; season withsalt and cook, stirring often, until tender (donot brown), 10-12 minutes.
6. Transfer to asmall bowl and set aside.
7. Butter a 3-quart gratin dish with remaining1 tablespoon butter.
8. Layer 1/3 of potato slices and1/3 of celery root slices evenly over bottom ofbaking dish. Cover with 1/3 of leeks, then 1/3of Gruyère.
9. Sprinkle with salt, pepper, and1 teaspoon thyme leaves. Repeat layers twicemore. Strain cream mixture into a mediumpitcher and pour over vegetables.
10. Set gratin dish on a large rimmed bakingsheet and cover tightly with foil.
11. Bake for1 hour. Carefully remove foil; continuebaking until top is golden brown and sauceis bubbling, 25-30 minutes. DO AHEAD: Canbe made 2 hours ahead.
12. Let stand at roomtemperature. Tent with foil and rewarm in a300° oven until hot, about 20 minutes.