1 pint heavy cream
4 sprigs fresh thyme
15 whole black peppercorns
5 garlic cloves, smashed
Coarse salt
Freshly ground black pepper
3 to 4 ounces fresh whole truffles

(white are in season, but expensive. Black summer truffles will work as well. Canned summer truffles will also work. Lastly, you can use dried powdered porcini mushrooms).

5 medium Idaho potatoes, peeled and cut into 1/8-inch-thick slices
Unsalted butter for baking dish

Place cream into a saucepan over high heat. Add the thyme, peppercorns, 3 cloves of garlic. Season with salt and pepper. Bring to a boil, then immediately lower to a simmer. Simmer for 15 to 20 minutes. For the final few minutes of cooking add the remaining garlic. Strain the mixture, discard the solids and set aside. If making in advance, it can be made up to this point 24 hours ahead of time and kept, covered, in the refrigerator.

Preheat oven to 375 degrees F. Lightly butter a 12-inch baking dish, 2 inches deep. Cover the bottom of the pan with a layer of the potato slices. Dust lightly with salt and pepper, and spoon some of the cream mixture over the potato. Repeat until pan is half full. Slice truffles thinly and lay over the top of the potato.

Repeat the potato layer, and gently press down on the potato until the cream comes to the top. (Fill pan to just below the rim.)

Cover with aluminum foil and place in the preheated oven. Bake for 35 to 40 minutes. Remove the foil and cook until the top is browned or the gratin is done. (The gratin is done when a knife slips easily into the center).