Water Cooler: Beginner’s guide to onions

Onions are versatile, cheap and delicious. With so many varieties of onions and other similar vegetables in the allium family, it can be hard to know which is best for a specific recipe and cooking method.

The allium genus includes hundreds of species, but the most common culinary varieties include onion, shallot, leek, chives, garlic and scallion. Their flavors can range in intensity, but they all have chemical compounds derived from cysteine sulfoxides, which is what creates that classic onion and garlic taste and smell. Allium plants have a bulb and leaves. The bulb is what is most often consumed. The leaves are usually edible although more bitter and fibrous, so they are often used as stock scraps.

Learning the subtle differences between the varieties will help you understand their best uses. Here are a few common varieties of onions and alliums that beginner cooks should know the differences between.

Yellow onions are the workhorse of the kitchen. Their classic onion tastes makes them versatile for a variety of cooked recipes, such as stir-fry, soup, stew, curry and for caramelizing. They have an intense flavor and are not sweet off the bat, but cooking them for a long time on low heat will mellow and sweeten their flavor. They are not often eaten raw. Yellow onions make a fantastic pantry item because they are cheap and can store for months as long as they are kept in a cool, dark and well-ventilated area.

Red onions are another popular choice and are frequently in their raw form for sandwiches, salads, garnishes and pickling. They are just as intense as yellow onions, but have much more sweetness to balance out their flavor. Their bright purple-red color makes them an attractive addition to meals, especially in a green salad. They can be transformed into a tangy, magenta garnish when pickled. Add pickled red onions to just about anything, such as breakfast bowls, rice bowls, stir-fry, tacos sandwiches and salads, to add a pop of color and delicious, sweet and sour crunch.

White and sweet onions have lower sulfur content, giving them a mellow flavor that is paired with a lot of gentle sweetness. They are great in large chunks for skewers, or work excellently in their raw form.

Dice them and sprinkle them on some tacos, bowls or soups or use them to make fresh salsas and dips like pico de gallo.

Shallots are not onions, but they are almost like a gourmet red onion. Their flavor is significantly more delicate which allows them to be used raw in things like salads, dips or aiolis, but they also take on excellent flavor when cooked. They mellow and sweeten with cooking like onions, but they have a subtle garlic flavor as well that makes for deeper flavor development with heat.

Green onions, also known as scallions, are actually a regular, bulb-forming onion, but they are harvested early before the bulb forms. There are other varieties as well that do not form bulbs. They have a mild and fresh flavor, with the white part of the scallion being more intense in flavor than the green part. Spring onions are similar, but they have small bulbs at the base and come specifically from bulb-forming varieties. They usually planted in the late fall and harvest in spring, so they are more mature than scallions, like a middle ground between scallions and onions. That said, their names are often used interchangeably. Scallions are light and grassy, making them a fantastic raw garnish, whereas spring onions have more bite and are great when sauteed and used in things like soup or frittata.