A shallot, which is a type of onion, looks like a small, elongated onion but with a milder flavor and a hint of garlic. Typically, it is a small bulb with copper, reddish, or gray skin. If you're lucky enough to have shallots in your pantry and before you start substituting them for onions, it's important to understand exactly what a shallot is.
From the outside, a shallot looks a bit like a misshapen red onion, but once you peel it, you will see that instead of rings, it divides into cloves as garlic does. Small shallot bulbs will have two to three individual cloves and large shallots can have up to six cloves. Each clove is flat on one side and rounded on the other.
In some recipes, it is hard to determine whether the entire shallot bulb is needed or if the number count in the ingredient list refers to the number of shallot cloves. In general, if the recipe calls for one shallot, use all the cloves within that single shallot bulb.
A member of the allium family–along with onions, garlic, scallions, leeks, and chives–the shallot is one of the milder of the group. The flavor can be described as a little sweet, with hints of garlic. Since it doesn't have the same bite as onion, shallots are ideally used raw in a salad or dressing, and won't overpower more delicate dishes.
Shallots vs. Onions
If you happen to have shallots in the pantry but your recipe calls for onion, you can substitute one for the other. This switch will come in handy if you are cutting a recipe in half and don't want to use only part of an onion. The general rule of thumb is for every small onion, use three small shallots. Just remember the taste will be milder and less "oniony."
What might more likely happen is that your recipe calls for shallots but you only have onion. Unfortunately, this swap only works if the shallots are to be cooked—raw onion tastes nothing like raw shallot. If substituting for cooked shallot, calculate a similar ratio but add a little bit of garlic to the measurement of onion to provide that hint of garlic found in shallots.
Shallots vs. Scallions
By looking at them, it seems unlikely shallots and scallions would be confused with each other. A scallion is long and thin with green leaves and a white tip and a shallot looks like a small, elongated red onion. Perhaps the mistaken identity persists due to the fact that they are both a type of onion and start with the letter "s." It also could be because shallots are referred to as scallions in some areas of the country, particularly in Louisiana. Early French settlers most likely had to substitute green onions for shallots, hence the confusion.