If you prefer leaner bites, trim off some of the excess fat. Slice the short ribs against the grain into 1½-inch (3.8 cm) chunks.
In a large bowl, combine the short ribs with the ingredients from soy sauce to gochugaru, if using. Gently toss and massage the beef so the marinade coats each piece well.
For thick-cut short ribs, about 1½ inches (3.8 cm) thick, marinate for at least 1 hour and up to 3 days in the fridge.
For thinner-cut short ribs, about ¾ inch (2 cm) thick, marinate for at least 30 minutes and up to 3 days in the fridge.
Air fry the short ribs
Preheat the air fryer to 320°F (160°C). Lightly spray the basket with oil.
Let the excess marinade drip off the beef, then place the pieces in the basket with a little space between each one. Lightly spray the tops with more oil. Cook in batches if needed.
For 1½-inch-thick pieces, air fry for 9 minutes for medium-rare or 10 minutes for medium.
For ¾-inch-thick pieces, air fry for 7 minutes for medium-rare or 8 minutes for medium.
Reduce the marinade sauce
While the beef cooks, pour the leftover marinade into a small saucepan. Bring it to a boil first, then lower the heat and simmer for 5 to 6 minutes, stirring often, until the sauce is slightly thickened.
Serve
Transfer the short ribs to a serving plate and let them rest for 5 to 8 minutes.
Slice each piece against the grain before serving. Garnish with scallions, sesame seeds, and a few spoonfuls of the sauce reduction. Serve hot with extra sauce on the side.
Video
Notes
About using the leftover marinade as sauce
Because the marinade has touched raw beef, bring it to a full boil first. Then lower the heat and simmer for 5 to 6 minutes, or until slightly thickened.
For an easier option, reserve a few tablespoons of the fresh marinade before adding the beef, then reduce that reserved sauce separately.
If the beef has been marinating for more than 3 days, discard the used marinade.
How long to marinate boneless short ribs
For thick-cut boneless short ribs, marinate for at least 1 hour and up to 3 days in the fridge. Overnight gives the best flavor.
For thinner-cut pieces, 30 minutes is enough, but you can still marinate them longer for deeper flavor.
Make-ahead, storage, and reheating
Make-ahead: Slice and marinate the beef up to 3 days in advance.
Freeze: Freeze uncooked beef in the marinade for up to 2 months. Thaw overnight in the fridge before air frying.
Storage: Store cooked short ribs in an airtight container in the fridge for 3 to 4 days.
Reheat: Reheat in the air fryer or oven at 320°F (160°C) for 3 to 4 minutes, or until warmed through.