Onions are used in a number of recipes that call for various shapes and sizes of the root vegetable, from slices to minced pieces. Learning the proper way to quarter and cut an onion is a valuable chef skill. A recipe may require you to quarter an onion and add the whole quarter to enhance the flavor of a sauce or roast. The technique of quartering an onion before chopping it into smaller pieces allows for similar-sized onion pieces, which promote an attractive presentation and even flavor of a dish.
Wash the onion under cold water. Place the onion on a cutting board.
Cut the stem end of the onion off with a chef's knife. Peel back the dry outer layer and the top skin layer of the onion and discard.
Keep the root end attached to the onion to keep the onion in place for slicing. Cut the onion in half vertically. Cut each half vertically to quarter the onion into 4 pieces. Remove the root end from each quarter piece of onion.
Slice each quarter vertically to create long slices. Slice each quarter vertically and then horizontally to dice (create small square pieces). Chop the pieces into smaller pieces to mince the onion.
Use a sharp knife to quarter the onion. If the knife is dull, it could slip while cutting the onion and result in injury.