Stewed turnips are a meal made from turnips and embers from a fire (only a fireplace will do). The meal only requires one turnip, but you can use multiple turnips. Note that this meal requires neither water or a pot. Stewed turnips don't relieve too much hunger (about the same as blanched mushrooms) unless you eat half a dozen, but they are very easy to cook.
As of v318, stewed turnip is no more. Either you cook a dish with turnip as veggie in it, or you eat it raw. Eating raw turnip alone is a very slow way to get starvation.