2 cups heavy cream
1 1/4 tsp salt
1/4 tsp freshly ground pepper
1/4 tsp freshly grated nutmeg
6 large russet potatoes, peeled and cut crosswise into 1/16" thick slices
4 oz Gruyere cheese, shredded (I used 6 oz)
1 Tbs chopped fresh flat leaf parsley
Preheat oven to 350 degrees. Butter a shallow 2-quart ceramic baking dish.
In a large bowl, combine the cream, eggs, salt, pepper, and nutmeg and whisk until just blended. Add the potatoes and toss gently until evenly mixed. Transfer to the prepared baking dish. Using your fingertips, spread the potatoes in an even layer, pressing them lightly so the absorb the liquid. Sprinkle the cheese and then the parsley evenly over the top.
Cover the dish tightly with aluminum foil and bake for 45 minutes. Remove the foil and continue baking until the top is golden, the gratin is bubbling, and the potatoes are tender when pierced with a knife, 15-20 minutes more. Let stand for 10 minutes before serving.