Onion Potato Gratin

1. Preheat oven to 400°F
2. Boil the potatoes:

   Boil the potatoes for 4 minutes in salted water (1 tablespoon of salt for 2 quarts of water). Drain and set aside.
3. Sauté the onions, sprinkle with salt and herbs:

   Heat the butter over medium-high heat in a large sauté pan and cook the onions, stirring occasionally, until they are softened, about 5 minutes.

   Sprinkle them with salt and the Herbes de Provence. Turn off the heat and set aside.
4. Layer potatoes, cheeses, onions, nutmeg in baking dish, pour over with half and half:

   Spread half of the sliced potatoes over the bottom of an 11x7-inch baking dish (Pyrex works well). Sprinkle well with salt and white pepper.

   Sprinkle with about a third of the Gruyere and Parmesan cheeses. Top with the onions, the nutmeg and another 1/3 of the cheeses.

   Layer the remaining sliced potatoes on top of the cheeses.

   Pour the half and half over everything. Sprinkle again with salt and pepper.

   Sprinkle the remaining one-third of the cheeses over everything. (At this point you can make a day ahead, just cover and refrigerate until time to cook.)
5. Bake:

   Bake uncovered in 400°F oven until cream thickens and everything is nicely browned, about 25-30 minutes.

Links:

Butternut Squash and Sweet Potato Gratin - from Pinch My Salt

Truffled Chanterelle, Celery Root and Potato Gratin - from 101 Cookbooks