Preheat oven to 400 degrees F. Generously butter a 13x9x2-inch glass baking dish.
Arrange 1/2 of the potato slices on the bottom of the prepared baking dish, overlapping slightly. Sprinkle generously with salt and pepper. Spread 1/2 of the creme fraiche over the potatoes and sprinkle 1/2 of the grated Gruyere cheese over the top. Top with the remaining potatoes slices, overlapping slightly. Sprinkle generously with salt and pepper. Spread the remaining creme fraiche over the top and sprinkle with the remaining Gruyere cheese.
Bake, uncovered, 30 minutes. Reduce oven temperature to 350 degrees F. and continue to bake the gratin until the potatoes are tender when pierced with a fork and the top is a golden brown, approximately 30 to 45 minutes. NOTE: Cover with aluminum foil if potatoes become too brown. Remove from oven and let stand 10 minutes.
Sprinkle the chopped parsley over the top and serve.
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.
Potato Gratin with Gruyere and Creme Fraiche Recipe: https://whatscookingamerica.net/lindasandberg/vegetables/potatogratin-cremefraiche.htm