Shallots and scallions are often confused and used interchangeably. But although they are both in the onion family, they're very different varieties of onion. You can substitute one for the other in many recipes, but the resulting flavor is quite different. When shopping for shallots or scallions, look for distinct differences.
Scallions are the shoots from any variety of white onion that is harvested before the onion bulb has formed. They are not the same as green onions, although the two are often confused. Shallots resemble small onions when mature and you can distinguish them from other onion varieties by their bulbs, which are made up of cloves similar to garlic. The individual bulbs are not covered by a membrane though, as with garlic. Like other varieties of onion, shallots have a thin outer layer of skin that dries. Scallions grow mostly upright and have hollow green tops that are paler, growing to white as you get to the root, which is not a fully developed bulb. Shallots grow similar to garlic in clusters with a head, or bulb, that contains multiple cloves.
Scallions can be cooked and used in many recipes, but may also be eaten raw. They're also used in salads and as garnishes. Their green tops are as valued as the white bottoms in cooking. Shallots are used dried or fresh, as other onion varieties are, but only the bulb is used. They may also be pickled and stored for up to six months.
Shallots taste like a mixture of onion and garlic, but are heavier on the onion taste. Scallions have a subtler onion taste that can be described as milder than a green onion, but stronger than chives.
Although many believe scallions are a variety of onion, they are really the immature plant of any variety of bulbing onion, meaning they're harvested before the onion has fully formed. Often scallions are called bunching onions, because they're sold in bunches. Shallots are available in two main types. The French-Italian shallot has a brownish-red skin and includes the Pikant, Atlas, Ed's Red and Creation varieties. These shallots can be used dried or fresh. The second type of shallot is the Welsh shallot, which includes the Louisiana Evergreen variety. Welsh shallots are often used in salads, as seasonings or for appetizers.