Add ground beef to a bowl and season with green onions, chili garlic paste, soy sauce, Kewpie mayo and garlic powder. Mix until well combined.
Roll ground beef into balls and set aside. Heat a cast iron skillet or griddle over medium-high heat until hot.
Spread Kewpie mayo on the cut sides of the burger buns, then toast them on the skillet until golden brown.
Place a beef ball onto the skillet and immediately smash it down with a burger press or plate until thin.
Flip the burger and cook for another 1-2 minutes. Add cheese if desired and let it melt.