1. Preheat the oven to 375º.

2. In a saucepan, heat together the cream, roasted garlic and thyme until steaming. Set aside while preparing the vegetables.

3. Lightly butter a baking or pie dish. Place a layer of the sliced potatoes on the bottom of the dish in a concentric circle. Season with salt and pepper to taste, ladle about 1/4 cup of the infused garlic cream on top, and finish with a sprinkling of the Gruyere cheese.

4. Make the next layer using celery root, and continue in this fashion until the baking dish is full. Note: Be sure to save enough cheese for sprinkling on top.

5. Top the gratin with Gruyere cheese and cover with foil. Bake on a parchment-lined sheet tray for 30 minutes. Tip: Lightly brush the inside of the foil with grapeseed oil to prevent it from sticking.

6. Uncover the baking dish and continue to cook until the potatoes and celery root are knife-tender and the cheese is golden brown and bubbly, about 30 additional minutes.

7. Allow to cool for 10 minutes, cut into slices and serve.

Notes:

• These can be made individually in ramekins, which will take half the time to bake.
• To roast garlic, slice the top off a whole head of garlic to expose the cloves. Place it in a small oven-proof dish, drizzle with a tablespoon of olive oil and cover with foil. Bake at 350º for 40 to 50 minutes, until the cloves are soft and a light golden color.