Pommes Dauphinoise and potatoes au gratin are pretty much the same thing. Both have thinly sliced potatoes baked in cream and/or milk and generally (though not always in pommes Dauphinoise's case) get a nicely browned topping of cheese. The differences manifest mainly in, say, an the choice of cheddar over Gruyère for a Midwestern potatoes au gratin... and maybe in the amount and type of cream... but otherwise they are functionally identical. It's an extremely simple dish in preparation, and the primary difficulty comes from the possibility of curdling the milk or cream while baking. It seems this is mainly an issue if you are using milk with a low fat content and baking at high temperatures... and this can be ameliorated by making a béchamel sauce with some additional flour and butter... but for this Dorie Greenspan recipe, we're using heavy cream and baking at 350 so that is not much of a worry. The other, very much related issue, is uneven and incomplete cooking of the potatoes which, for those of us without uber knife skills, is mainly a result of not using a mandoline/v-slicer. I hate to be all "kitchen gadgety" but... along with making french fries at home... a gratin is one of those dishes that can basically make the case for owning a mandoline all by itself. Peeling and thinly slicing two pounds of potatoes is good knife practice, certainly, but it also takes a hella long time and makes the dish less appealing to prepare on a regular basis... however, given the amount of calories in a serving of pommes Dauphinoise, you may find that to be a feature not a bug. I've used a food processor to do this kind of slicing in a pinch, but I've found our slicing attachment to not be very reliable in getting uniform pieces... and if I'm not getting uniform pieces I feel like I might as well get some knife work in. However you may have a much better food processor than me (not at all unlikely) and find that to be the best choice. Probably worth a shot at any rate.
Also, as a specific note for this recipe, Dorie Greenspan called for a 9" deep dish pie plate or 2 quart baking dish. That's going to be a very deep and thick gratin, which is not my personal preference, so I went with a 3 quart dish (a 9x13x2 pan) to give a little more surface area (and browned cheese!). From what I've read I don't think you really want to go more than 3 or 4 rows deep if you want uniformly cooked potatoes, and we were best able to accomplish that with a larger area pan. As always, YMMV.
So, as mentioned above, this recipe is from Dorie Greenspan's Around My French Table.
- 2 lbs of high starch potatoes (e.g. russet), peeled, sliced 1/8" thick
- 1 3/4 cups heavy cream
- 3 cloves of garlic, minced
- Salt and Pepper
- Light cream or whole milk, as needed
- Small sprigs of thyme and/or rosemary
- 4 oz Gruyère, grated
- Put a rack in the middle of the oven and preheat said oven to 350 degrees.
- Butter at least a 2 quart baking dish (see dish conversions here) and put it on a cookie sheet (for spills/overflow and ease of maneuver).
- Bring the heavy cream and garlic to a simmer over low heat and keep warm, but not simmering, while you prepare the baking dish.
- Place potatoes in overlapping rows/concentric circles, salting and peppering each layer, spooning over the cream and garlic mixture until it laps the sides of the potatoes. Continue this until you've placed 4 layers of potatoes.
- If you run out of heavy cream, use light cream or whole milk to make sure liquid is just peeking out at the edges of the pan.
- Separate the herbs from their woody stems and sprinkle over the potatoes. Top with the cheese.
- Bake for 45 minutes. If a knife pierces the potatoes easily to the bottom (in several spots) it's done, otherwise bake until the potatoes are tender: 15 to 30 more minutes. If you notice the top is starting to get too brown at any point, just cover it with foil.
- Once the potatoes are tender enough, turn off the oven and open the door, allowing the gratin to rest 5-10 more minutes in the warm oven.