A holiday meal is a time to bring on your best with lots of flavor and worry about the calories later. That’s where the blue cheese comes in; it is heavenly in this gratin. This dish makes a wonderful rich side at the holiday table, but it is also a vegetarian dish that can be served with simple salad for a meal on its own. Serve with Cherry CiderYield: 6-8 servings1 pound celery root, peeled, cut into 1/8-inch thick slices 1 1/2 pounds russet potatoes, peeled, cut into 1/8-inch thick slices 1 large tart apple, peeled, cored and cut into 1/8-inch thick slices Coarse salt and freshly-ground pepper 1 1/2 cups crème fraîche, stirred to loosen 6 ounces of your favorite blue cheese (I like Bleu d’Auvergne)Preheat the oven to 400°F. Generously butter a large, oven-proof baking dish. Arrange half of the potato slices in the bottom of the prepared dish, overlapping slightly. Sprinkle generously with salt and pepper. Scatter half of the apple slices over the potato, then arrange half of the celery root slices over the apple, overlapping slightly. Sprinkle generously with salt and pepper. Spread half the crème fraîche over the apples and sprinkle with half of the cheese. Top with the remaining potato, apple, and celery root, salting and peppering each layer. Spread with the remaining crème fraîche and sprinkle with the remaining cheese.Bake the gratin uncovered for 20 minutes. Reduce the oven temperature to 350°F. Continue to bake until the potatoes are tender and the top is golden brown, about 35-45 minutes. Remove from the oven and let cool for 10-15 minutes. Serve warm.