Though people consume only the bulb of most onions, they regularly eat the bulb, stalk and leaves of scallions. Every part of the scallion is mild in flavor and tender, unlike the rough stalks and overall pungent flavor of larger onions. Scallions are suitable to eat raw or cooked. To prepare them for consumption, you must trim them appropriately to remove sections that detract from the flavor. Once you remove the undesirable portions of the scallion, you can trim it several ways -- based on your recipe or aesthetic preferences.
Lay a scallion horizontally on a cutting board. Cut more than one scallion at a time by arranging them in a single layer, with their white bulbs aligned.
Hold a chef's knife vertically above the scallions. Slice through the white bulb in a single, smooth motion. Trim the bulb about 1/4 inch from the end. Do not include the roots in your 1/4-inch approximation.
Turn the scallion 180 degrees, to move the top of the stalk within reach of your dominant hand and the knife.
Slice through the tubular, green leaf 1 inch away from the end, to trim the top of the scallion.
Examine the scallion for areas that are wilted, dry or excessively dark. Slice these sections off the scallion, if any are present.
Slice through the middle of the scallion where the white and green sections meet to trim the bulb, if your recipe calls for green pieces only.
Snip the green, leafy section of the scallion with kitchen shears, to trim short rings for garnishing or cooking. Alternatively, slice through the section with a knife to yield the same results.
Hold the knife vertically above a horizontal onion, to trim pieces with straight edges. Or hold the knife diagonally above a horizontal onion, to trim pieces with slanted sides.
Lay the scallion vertically on your cutting board, to julienne it into long, thin strips. Hold the knife vertically, in the same direction as the onion, and slice the entire onion in half. Turn the halved onion sections so that their flat sides are on the board. Slice through the onion vertically, to cut fine strips.