I found this interesting article by Stacy Ballis quite interesting. Maybe you will too!
Alliums are not particularly sexy. You don’t find the members of the onion family proudly displayed up front, like seasonal fruits or whatever vegetable is having its moment in the sun. You might enter your grocery store to a pyramid of shiny apples, or a table laden with bunches of asparagus, sitting proud in icy tubs. You may encounter an array of heirloom tomatoes in all the colors of the rainbow. But the onion tubs will always be somewhere in the back of the produce section, one half-step down on the produce loveliness hierarchy from potatoes.
This does a complete disservice to the entire onion oeuvre. Onions and their kin are the workhorses of the kitchen. They form the base of nearly every culture’s flavor-building: a classic French mirepoix, Italian soffritto, Latino sofrito, or German suppengruen. Anyone from New Orleans will discuss with you at length the proper use of the Holy Trinity, and onions are a part of plenty of Asian dishes, both in the cooking and garnishing.
Onions come in a lovely variety of hues and textures, from pure white to deep purple, and in flavors that range from nearly as sweet and mild as an apple to powerful punchy, to deeply spicy. They range in size from tiny pearls to gargantuan orbs the size of a softball, and even come in a strangely flattened form from Italy, the lovely Cippolini.
Mixed in with your basic onions in almost every store are the shallots, which many people assume are really just a small version of the red onion. Their proximity and lovely lavender hue might make that a reasonable assumption, but the the shallot is an elegant European cousin to the rest of the onions we know and love so well, and a really terrific addition to your cooking.
While they are related, shallots differ from onions in some basic ways. First of all, unlike regular onions, which grow as single bulbs, shallots grow in clusters, more like garlic. They are a bit sweeter than regular onions, and their flavor is more subtle. This makes them especially good as a seasoning in raw applications like vinaigrettes or salads, where they add oniony flavor without too much punch, or in slow roasted or braised dishes, where their sweetness can really enhance a dish without watering it down.
Shallots come in a couple of different colors, the pale purple with brown skin being the most common, and the French gray shallot, which is rarely available and considered the ultimate in shallot superiority. Here in the States, you will almost always find the regular plain shallot, which is small and squat. But if you ever spot a banana shallot, sometimes called a torpedo shallot, which are much longer and straighter, grab them. They are easier to peel and I find they have a milder aspect that I just love. They are widely available in the markets in Europe, and I wish they were less of a specialty item here.
Regardless, while both onion and shallot give an oniony flavor, they are not actually interchangeable. If you are using them as an enhancement, measured in tablespoons, as in a salad dressing, you can swap them out with little issue. But in a bigger cooked dish, the general thought is that you should use half the amount of shallot as you would onion when making substitutions.
Whether you are making a dish that is very onion-forward, or just relying on an onion to provide a solid base to carry other flavors, adding fresh minced shallot as a garnish on your salad, or fried shallots on your next experiment with Thai cooking, the alliums will always have your back. They might not be sexy themselves, but your food can’t be sexy without them.