It's been over a decade since my halmuni (grandmother in Korean) passed away, and over two since I lived with her. Yet I hear her voice often, especially while I cook. She lived with us and spent most of her day in her garden and kitchen, where I often lingered.
"Cover the gochujang with the foil seal so that it doesn't oxidize. Always push the kimchi under its juices before putting it back in the fridge. A little drizzle of sesame oil will revive any banchan." I'm a better cook because of her. And I make the juiciest meatballs—all kinds, really—because of one thing she said to me every time she made mandu (Korean dumplings): "The onions must be grated."
Though I suspect my halmuni has never made a meatball in her lifetime, she's likely made tens of thousands of dumplings—the filling is essentially a meatball that is wrapped. And they were always juicy and so flavorful. Her trick was to grate a raw onion into the meat mixture, and it's the same trick I use to make meatballs.
How To Upgrade Your Meatballs By Grating the Onion
A good meatball recipe calls for an onion—or at a minimum, fresh garlic—for flavor, texture, and moisture. You could chop the onion, but if the pieces are too big, the meatballs can fall apart as they cook. Or you could finely mince the onion if you have great knife skills.
My halmuni taught me to grate the onion through the second smallest holes of a four-sided box grater. (If you don't have a box grater or are scared to scrape your fingers, pulse the onion in a food processor until you no longer see large pieces and it's mostly liquid and pulp.)
Before you add the ground meat or any other ingredient to the mixing bowl, grate the onion first, with the box grater set inside of it to catch the pulp and juices. You don't have to drain the liquid—it'll add moisture and flavor to the meatballs. The ground meat will suck up the liquid, expanding and lightening the mixture.
This is an easy and smart way to add flavor and moisture and a trick I use when making all kinds of meatballs. When a meatball recipe does not call for onions in the meat mixture, I still add half of a grated yellow or white onion.
My Trick for Shaping Meatballs Lightening Fast
I stole a trick from my baking days to shape meatballs quickly: use a cookie scoop. To make things go faster, use the scoop to portion the meat mixture onto a large plate. Then, once you've scooped out all of the meat mixture, roll each meatball between your hands. It's a lot more efficient than scooping and rolling them one at a time. As my halmuni said, "You'll become a slave to your kitchen if you don't work efficiently."