Like most people, I love potatoes. There is scarcely any variety or preparation of them I don't enjoy. But one of my favorites comes from as close to a bible as we have in the kitchen, Julia and Jacques Cooking at Home.
Pommes de terre boulangère is a gratin of thinly sliced potatoes, onion and garlic first parboiled then baked in a flavorful herbed stock. The potatoes release starch into the stock, which in turn thickens and forms an unctuous medium. The top layer browns and crisps, and the rest stays soft and yummy.
This is one of my all-time favorite side dishes; it goes especially well with a nice roast chicken. It is elegant, flavorful and above all else easy. Plus, the thickened stock gives a richness that implies creaminess, yet there is no dairy and practically no fat. This recipe is easily made vegetarian, even vegan, but replacing the chicken stock with vegetable stock or water, and is to the best of my knowledge gluten-free.
The one trick, if you can call it that, is to invest in a mandoline; a cheap Benriner does the job very nicely. You want thin, even slices of everything, and the mandoline accomplishes that with astonishing speed.
Use small, waxy potatoes, like Yukon golds or small white potatoes. I have also mixed up Yukons with fingerlings for some contrast in flavor and texture, and that works very well.
I have found that this is also a recipe that defies precision, so the measurements I give are rough at best. It is most of all about maintaining a balance between the amount of stock versus the potato mixture. Too much, and your gratin will be soupy; too little and it will be dry and tough. On the whole, though, it is better to err on the side of dryness when in doubt.