At its simplest, a gratin is merely thickly sliced potatoes, whole milk (or cream, even double, if you wish) and a few dollops of butter nicely spread on top, then oven! Add herbs or spices or both, and a handful of aged, grated cheese, stick it under the grill for a nice finish and you’re in heaven.
A few words on gratins first: the origin of the word gratin comes from the French verb gratter (to grate, I suppose before the potato was around, chefs would grate hard cheese to top up baked vegetable dishes such as Swiss chard, even artichokes). To qualify as a gratin, a dish has only to be finished under a grill (preferably) or in the oven, so that its top is browned (at the heart of the concept is simply food with something crusty on top, really). Well, there’s really more than that of course. A good potato gratin should be half crisp half chewey and redolent of caramelized flavors which have been enriched with a good stock (in my case, infused with fresh thyme) and a well chosen piece of cheese. I have done gratins with ordinary cheddar, Gruyere, Emmental, Fontina and even dabbled with the famous Spanish cheese, Manchego. I tried goat cheese once and the whole thing ended up as a mess…so don’t go there, unless you have to.
Because we are a complicated people we have a plethora of gratins in France: gratin Dauphinois, gratin Savoyarde, gratin provencal (made with vegetables) gratin Italian (made with mozzarella) and of course there’s a whole range of sea-food and game gratins to tempt the mere mortal. I have tried to gratinize (my word, I think) just about everything that is edible as it is a great way of using leftovers as well as allow a certain degree of creativity. More on that at the end of this piece.
To make a memorable gratin you need the right potato, a floury one if possible, with medium to low starch like the Yellow potatoes:
they are usually round to slightly oblong shaped potatoes with thin, yellowish light brown skins, and buttery yellow to golden waxy flesh. Yellow potatoes are low to medium in starch and have a moist, creamy, succulent texture with a buttery flavor. They are well suited for boiling, steaming, mashing, roasting, grilling, and au gratin dishes.
Yellow flesh potato varieties include Yukon gold, yellow Finn, German Butterball, Carola, Nicola, and Alby’s Gold. Ask your greengrocer to stock any of these and you’re rocking. So you have your potatoes of choice, now is the time to peel and cut. The slices need to be thin, to absorb as much sauce/stock as possible so that they cook through. I use a good Japanese knife to cut mine but any reliable mandolin would do the trick (also known as a “V slicer”). The dish in which you are going to cook the gratin is also relevant. A good gratin dish should not be deeper than one inch (2.5m). Le Creuset comes to mind when making a gratin of course but there’s no need to spend that kind of money unless you have it to burn. A simple glass baking dish is just as good.
There are many ways to make a gratin, everyone has a favorite, and this is mine, for 4 to 6 persons: first I preheat the oven to to 360ºF (180ºC), then cut the potatoes into thin slices. I butter the dish, then add some fresh thyme cut finely. Next I lay the slices down, overlapping, up to almost an inch. Then I add a mixture of lightly salted vegetable stock with slightly beaten cream (half and half, to make a liter or 2 pints), then I add my grated Emmental on top (a generous amount, at least 300 grams (a bit over half a pound) then I sprinkle it with freshly grounded black pepper, bake for half an hour, and under the grill for another 15 to 20 minutes, depending on the intensity.
Some people make a thick Bechamel sauce for this dish, I don’t because it makes a much more stodgier texture. But don’t let me stop you, it’s all good.
A variation everyone likes is the Savoyard version which cleverly uses onions and garlic to a great end. It’s even better if you allow the onions to caramelize properly as it will give the dish an incredible flavor. Just cut 4 to 6 medium-sized onions lengthways and 8 to 10 peeled garlic cloves roughly cut and bake slowly with a little olive oil till brown. This can take up to 3 hours. If you want to speed it up add a tiny amount of brown sugar and a knob of butter then watch it turn golden within the hour. I would use a different cheese like Fontina or Gruyere but if you can’t obtain any of these two, a good mature cheddar is just as good, and much cheaper. For this dish you would need at least 250 grams (8 and a bit ounces).
Prepare the potatoes and onions as above, drying the cut potatoes well. In a skillet heat up a pint of milk together with a pint of stock. Add some salt and pepper to taste. In the meantime rub your oven dish with a garlic clove then salt, then butter. Add one layer of sliced potatoes, one layer of onions/garlic and half of the milk-broth mixture. Sprinkle with half of grated cheese. Add the rest of the potatoes, onions, milk-broth mixture, and sprinkle with the rest of the cheese. I usually add 2 or 3 bay leaves to this dish but it’s not crucial if you don’t have any. Bring to a slow boil on top of the stove (though I wouldn’t do this with a glass dish, make sure it’s a metal one), dot with butter and bake for 30 minutes uncovered at 360ºF (180ºC)
And now for ideas and suggestions: I have made the following gratins in the past, and as I said above the only one that didn’t turn out the way I wanted was the goat cheese & sweet potato one. Here’s the list: smoked salmon & potato; wild mushroom, potato & Gruyere; leeks & potato (this beats the soup version); crab meat & wild rice topped with Emmental; scallops, mussels & mashed potato, topped with mature cheddar; all root vegetable gratin; smoked duck & baby potato; and one that you have to try once in a lifetime: a potato gratin flavored with truffle oil (you only need a few drops so intense is the flavor). Truffle oil is expensive and a small bottle (roughly 250 ml for $20) would last a couple of years, it’s a good investment.
I’m writing a piece on Italian food next.