Preheat oven to 400 degrees F. Place oven rack in the middle of the oven. Butter a 9-inch x 13-inch baking dish.
Remove rind and shred fontina cheese using a hand grater.
Place 1/2 the potatoes, overlapping slightly, in prepared baking dish. Salt and pepper slices generously. With a rubber spatula, spread half the creme fraiche over the potatoes. Then sprinkle 1/2 the cheese over the creme fraiche. Make a second layer in the same way using the remaining ingredients.
Bake potato gratin on center rack of your oven, uncovered, for approximately 30 minutes. Then lower heat to 350 degrees F. and bake approximately 30 more minutes or until potatoes are tender when pierced with a knife. Potatoes will have a golden brown crust on top. N OTE: Cover with aluminum foil if potatoes become too brown. Remove from oven and let stand 10 minutes.
Gratin can be prepared up to 4 hours ahead. Cool, cover loosely with aluminum foil and refrigerate. Reheat, covered with aluminum foil, in a preheated 350 degree F. oven until hot, approximately 20 to 25 minutes. Drizzle truffle oil over the top and sprinkle with herb just before serving.
Makes 8 servings.
* If you can not find creme fraiche, make your own by whisking together 1 1/4 cups whipping cream and 1/2 cup sour cream. Let stand at room temperature until thickened, approximately 6 hours or overnight. Cover and refrigerate. Can be stored up to 1 week in the refrigerator. Makes about 1 3/4 cups.
** Truffle oil is top-quality olive oil that has been infused with either white or black truffles. Both types of truffles have an earthy, mushroom like flavor. Truffle oil was originally created when truffles are soaked in olive oil. Before commercial truffle oil was introduced in the 1980s, chefs in Italy and France traditionally made their own by steeping tiny bits of fresh truffles in high-quality olive oil.
Potato Gratin with Truffle Oil Recipe: https://whatscookingamerica.net/vegetables/potatogratintruffleoil.htm