Onions: They’re in everything. Seriously, think about what you had for dinner last night. I’d lay odds that it had onions in it.
Perhaps onions’ ubiquity is the reason pretty much everyone agrees on the right way to chop them. As a species, humans have had enough experience with onions to agree, en masse, that it’s a bad idea to slice them fully before attempting to chop them. Rather, you should use the onion’s unique shape to your advantage to protect your fingers—as Jamie Oliver demonstrate in the video.
One quick note: This is not a video about how to dice onions. Dicing is a pointless activity on which no home cook should ever waste his or her time. Dicing aims to create cubes of exactly the same size—like I said, pointless. Chopping, on the other hand, aims to create pieces that are more or less the same size, which will suffice for 99.99 percent of your onion-related needs.