Preheat oven to 375 degrees F. Butter a 2-quart oven-to-table baking dish or gratin pan; set aside.
Cut off and discard base of cauliflower, then cut the head into small, individual florets.
Bring a large pot of water to a boil and salt generously. Add cauliflower florets to pot and cook until tender (but not mushy) when pierced with a sharp knife, about 5 minutes. Drain florets and thoroughly pat dry with a clean kitchen towel.
Place the drained and dried cauliflower in the prepared baking dish and toss with creme fraiche and half of the grated cheese. Season to taste with salt and pepper. Sprinkle remaining cheese over cauliflower, then top with bread crumbs and hazelnuts.
Bake on center rack of oven until cheese has melted and bread crumbs and nuts are golden, approximately 20 to 25 minutes.
Garnish with chives or parsley before serving.
Serves 5 to 6.
Creme fraiche is available in many supermarkets. If you can't find it, the following recipe works well. It needs to be made at least 6 hours in advance.
Whisk cream and sour cream together in a medium non-reactive bowl. Let stand at room temperature until thickened, 6 hours or longer. Cover and refrigerate. NOTE: Creme fraiche can be stored up to 1 week, covered, in refrigerator.
Makes about 1 1/3 cups.
* To toast hazelnuts, spread on a rimmed baking sheet and bake in a preheated 350-degree oven until browned and fragrant, approximately 6 to 8 minutes. Remove and when cool enough to handle, place nuts in a kitchen towel and rub together to remove as much of the skins as possible.
Cauliflower Gratin with Gruyere and Hazelnuts Recipe: https://whatscookingamerica.net/vegetables/cauliflowergratin.htm