I learned how to chop an onion many years ago at the only cooking class I’ve ever taken – a Knife Skills class I attended with my best friend, Marissa, in Chicago when I was right out of college. It was one of the most valuable learning experiences for a new home cook and I highly recommend it if you have a class in your community.
Now to the quick tip. To get started, take a sharp knife (it’s always important to use very sharp knives) and trim off the tip of the onion – the end opposite of the root. Stand the onion on this new flat end you’ve created and cut the onion in half – right down the root. Peel back the outer skins (and save them for stock!).
Lay one of the halves on your cutting board and press down on the top of the onion with the heel of your hand (I sometimes hold the onion down with my fingertips, too). With your other hand, use the knife to slice horizontally into the onion several times in evenly spaced cuts. Next slice down through the onion with evenly spaced slices. Finally, chop the onion right down to the root (and toss that root in your soup stock freezer bag, too.). Here’s a step by step visual of the chopping steps. My hand steadying the onion is missing in step 2 and 3 to hold the camera! But you definitely want a firm grip on the onion while cutting.
And one final note about onions. If you’re buying organic onions, I’ve read that you should store them in the refrigerator to keep them from sprouting too quickly.