How we tested
Tagines (the cooking vessel, not the stew) have lately enjoyed a fashionable comeback in cookware catalogs and food magazines. A shallower take on the Dutch oven, a tagine has a distinctive conical lid that makes for a dramatic presentation at the dinner table. According to tradition, the conical shape helps cooking performance as well: As steam rises during cooking, it condenses in the tip of the relatively cool lid (it's farther from the heat source than most lids) and drips back into the stew, conserving water in the process. Less steam loss means you can start off with less liquid to begin with and thus end up with more-concentrated flavors. Or so the story goes.
To put this theory to test, we brought equal amounts of water to a simmer in three tagines—a traditional terra cotta model and two modern versions—put the lids on, and let the water "cook" over low heat. We included our favorite Dutch ovens for comparison. After one hour, we measured the water left in each of the pots, and it was clear that the tagine's conical shape was not such an advantage after all. The big losers—literally—were one of the Dutch ovens and the traditional terra cotta tagine, which lost 16 percent and 30 percent of their water, respectively. (By contrast, the others lost only 8 to 9 percent.) More important than the shape of the pot were the lid's weight and fit: The leaky Dutch oven had the lightest lid, while the base and lid of the handmade terra cotta tagine simply didn't fit together as precisely as their machine-made counterparts.
What does all this loss mean when it's more than water cooking? Not much, said our tasters, after sampling five batches of Moroccan chicken. Although the amount of liquid left behind in the stews varied, that variance translated to little discernible flavor difference. If you're a stickler for tradition, choose a tagine with a heavy, tight-fitting lid. But a Dutch oven will do the job just as well.