My Little Corner of Culinary Basics

Cook's Illustrated: How to Roast Root Vegetables

Roasting vegetables evaporates much of their water, concentrating their natural sugars and yielding a rich, sweet taste and meaty texture. Roasting also gives root vegetables a crisp, golden skin that makes a wonderful contrast to their soft, moist interior.

I wanted to find an easy way to roast a lot of root vegetables at one time--cut them to size, throw them into the oven, and, aside from an occasional stir, forget about them until they're cooked. I experimented with a variety of cut-up root vegetables: potatoes, sweet potatoes, white turnips, rutabagas, carrots, and parsnips. I added onion, shallot, and garlic for flavor. (I also experimented with beets, but found that they roast best when left whole.)

Different vegetables have different ideal cooking temperatures, so I devised a master recipe, roasting at 400 degrees F, that represents a compromise. Potatoes and sweet potatoes cooked beautifully at 400 degrees, browning well on the outside and staying soft and luscious on the inside. Turnips, rutabagas, carrots, and parsnips, however, shriveled a little at that temperature; they do better at 375 degrees for 30 minutes to cook them through, with a final roasting at 425 degrees for 15 to 20 minutes to brown them (see below recipes for individual vegetables). I also tried roasting at 450 degrees for 15 minutes, then reducing the temperature to 350 degrees for the remainder of the cooking time, but none of the vegetables browned well.

The rules that apply to roasting meats also apply to roasting vegetables: you need high, dry heat and a low-sided roasting pan that is large enough to accommodate the vegetables without crowding. In addition, the vegetables, with some exceptions, must be cut to roughly the same size for even cooking. What the pan is made of is much less critical than its size; vegetables brown well in aluminum, Pyrex , enameled steel, and even porcelain, but a too-small pan will enormously inhibit browning. This browning, or caramelization, is important for reasons of both sight and taste: not only is the golden-brown color attractive, it is also evidence that the natural sugars in the vegetables have caramelized, adding a rich, deep, concentrated sweetness.

You also need some fat to roast vegetables well. For about a pound of vegetables, I use at least 1 tablespoon of butter, vegetable oil, or olive oil; chicken or duck fat is especially wonderful. You can, of course, combine more than one fat. I found that vegetable oil (I used canola) gave the lightest, crispest crust; olive oil browns a little less well but adds a nicer flavor. Butter keeps the vegetables moistened and makes a softer crust; it also lends a superior flavor. A combination of butter and oil browns better than butter alone but not as well as oil alone; the butter flavor is not particularly noticeable. My recommendation: for visual appeal, choose vegetable oil; for flavor, olive oil or butter. You can hardly go wrong, regardless of your choice.

This recipe is devised for roasting any combination of the following root vegetables: carrots, parsnips, all-purpose or boiling potatoes, sweet potatoes, rutabagas, and turnips, along with yellow or red onions, shallots, and garlic. Do not go overboard, however; too many vegetables muddy the flavor. I usually limit the mix to two or three root vegetables. Cut all vegetables, as necessary, so that they are about 1-1/4 inches thick.

If you wish to parboil the vegetables before roasting, follow the procedure described below in Parboiling: Is It Worth It? before beginning the master recipe. Season the vegetables with pepper only after roasting--pepper becomes strong and bitter with prolonged cooking.

When roasted individually, carrots, parsnips, rutabagas, and turnips should cook at a lower temperature to start; at higher temperatures, they dehydrate and shrivel. (The roasted turnip and carrot recipes that follow give specific cooking times and temperatures.)