The Time is Right for Gratins

With summer here, the time is perfect for gratins. Sure, everyone is firing up the grill, but let’s face it-grilled vegetables only hold their appeal for a while, and then you want something with a little more depth of character. All those vegetables that are great on the grill are also great in a gratin. Easy to make, gratins can be made in advance and will keep overnight, and are good hot from the oven, or at room temperature. What’s not to like?

So, what is a gratin, anyway? The word gratin means three things in the kitchen; 1) It is a dish or preparation, usually consisting of layered or overlapping slices of something, cooked in the oven in a dish that is a shallow baking dish that is called a gratin. 2) A baking dish or vessel used for cooking gratins, usually oval in shape, usually around 1½ inches deep, usually ceramic or enameled cast-iron. That said, restaurants use stainless-steel “hotel” (rectangular or square) pans. Pyrex casserole and baking dishes work great also. 3) To cook something “au gratin” or to “gratinee” something means to cook it until it is browned on top. Sometimes this is done under the broiler, but do not attempt to broil Pyrex or it will probably shatter in the oven.

Most people are familiar with potatoes au gratin, a.k.a. scalloped potatoes, but that is as far as it goes for gratins. For me, that is just the beginning. As much as I love that dish, in summer I want something lighter without the cream and all that melted cheese. If I am in the mood for a potato gratin, I slice up something like Yellow Finns or some fingerling potatoes, and then layer them into a gratin dish, usually on top of some onions sautéed until soft and golden. Salt and pepper, herbs, a healthy drizzle of olive oil, and then I pour vegetable stock into the pan to come to just below the top of the potatoes. I then cook the dish in a 450°F oven until the potatoes are soft, and the top is golden. All of the liquid should have been absorbed as well. Sometimes I scrape some cheese over the top of the dish about ten minutes before it is done.

Where this dish really takes off for me is when I have a bunch of summer vegetables to play with. By summer vegetables, I mean things softer than roots, things like eggplant, summer squashes, and tomatoes. Plenty of fresh herbs like basil, oregano, and sage help things along in the fragrance department, too. You can also do a gratin with fennel bulbs, and with chard-using both the stems and leaves, or just the stems. The thing to remember is you will need some source of moisture for the gratin while it cooks, whether it is from the vegetables (think tomatoes), olive oil, stock, or cream. When I build a gratin I think of what will give the moisture so the vegetables soften, and then what will give sugars so the vegetables sweeten and caramelize. This is one reason I almost always use a base of sautéed onions, as they provide some of that lubrication, the other is the depth of flavor they give. To keep it simple and make it quick, I’ll use soffritto from the refrigerator or freezer if I have it. Soffritto is a sauté of onions, celery, carrots and/or fennel that has been cooked down to a soft golden color (or darker for some uses) that stores easily in the freezer and can be the base for so many things.

Here is the basic structure for a gratin; base layer of sautéed onions and garlic, overlapping layers of vegetables, drizzle of olive oil or some stock, seasoning. For the overlapping vegetables- cutting them ¼ inch thick is pretty much standard, and when you overlap them, they should cover each other by 2/3rds.  You may need to cut pieces smaller to fill in large spaces, and this is fine. I usually save the end bits for this purpose. When cutting the vegetables, I always slice on the diagonal. There are two reasons for this; the first is that the longer slices allow for easy overlapping and layering, the second is that the diagonal slices give a larger bit if skin to show off the pretty colors of summer. When I lay the slices in the gratin, I always turn them so the outside surface of the vegetable is facing up. This ensures a nice colorful dish, and also ensures there is more vegetable in contact with vegetable so the dish melts together instead of just drying out.

When making your gratin, you get out your product, and a gratin dish. Heat the oven to 400°F. Heat a pan over medium-high heat. While that happens, slice two onions up. When the pan is hot add two or three tablespoons of oil and heat it up. Add the onions and toss to coat with oil. Turn down the heat to medium-low and cook the onions. While the onions cook, slice the vegetables. Let’s say you have tomatoes, 1 each yellow and green zucchini, and one Japanese eggplant. Slice each vegetable into ¼ inch slices (watching the onions and tossing them to avoid burning, cooking until just golden and evenly soft.) and keep them separated by type. Rub the inside of the dry gratin dish with a large garlic clove, rubbing with enough force to smear the inside with a visible sheen of garlic juice, and allow to dry for 2 minutes. Very lightly oil the gratin dish. When the onions are done, put them in the gratin dish. Then start layering the vegetables in, being sure to overlap by 2/3rds. Start at one end with the eggplant, then add tomatoes, the squash, then eggplant, tomato, etc. While layering in the vegetables, don’t forget to sprinkle or tuck some herbs in. Sprinkle with some chopped oregano or slip in some basil leaves as you go. When you have reached the end, pat the vegetables down a little, then drizzle with some flavorful olive oil, season with salt and fresh ground pepper, then into the oven. Bake for 25 to 30 minutes, or until golden and tender. If the gratin seems done, but not brown, try moving the gratin to the top shelf of the oven. Remember-heat rises so it is hotter up there, and the reflected heat should serve to “gratinee” the dish. Serve hot from the oven, or serve room temperature. May be made ahead of time and reheated if you wish. It really is that simple.

You can make gratins with things that are firmer like fennel bulbs or thick chard stems, or potatoes as mentioned earlier, as long as you add some liquid. The liquid is there to “stew” the dish and soften up the hard cell walls of the vegetables, and then to evaporate so the sugars can then caramelize. For things like fennel or chard, lay down some cooked onions in the dish, then layer in the chard stems or quartered and cored fennel bulbs, then add some stock and a little white wine to come half-way up the gratin, then bake. You can also sauté diced chard stems with diced onions and sauté them with scads of garlic, and then lay them into a gratin dish, and then wilt the chopped chard leaves in the same pan with a little vinegar and red wine. Lay these on top of the stem mixture and top with enough breadcrumbs to cover the dish. Before topping the dish with the breadcrumbs, add a little olive oil (a tablespoon should do it, just enough to moisten the crumbs) and herbs to them. This will impart flavor and color to the topping and help prevent it from burning. Cook the gratin just to heat through and color the top. I sometimes prep this dish (up to topping with the crumbs) the night before or in the morning, and then just top and bake at service for a quick side. This type of dish is good at room temp or even cold, and as funky as it sounds, makes a good sandwich with some fresh mozzarella, tomato, and tapenade on a soft roll.

For gratin combinations, think tomato and zucchini, tomato and eggplant, artichoke potato (this takes a little more work but is great!), different colors of summer squash, fennel and tomato, thinner slices of summer squash with just wilted escarole. You can even work peppers into gratins-just be careful if they are spicy. Gratins are an easy dish to learn, and the rewards are huge. Gratins work well in other times of the year as well. You can make gratins with sliced winter squashes, cardoons, even leeks. In winter, using cream in the gratin makes a rich welcome dish when it is cold, but remember you can always use stock instead.

Gratins need not be elaborate. If you have some already cooked onions in the refrigerator, (I tend to grill extra onions during summer for this sort of thing) or some soffritto, you can put a gratin together in 10-15 minutes, and have it on the table in another 30. Fry a couple fresh eggs to top it off, some bread to mop it up, and you have a quick supper. It’s that simple.