- Slice off white parts of green onions and thinly slice the greens into strips using a sharp knife or green onion slicer. Soak greens in cold water for 5 minutes, drain and blot dry with paper towel.
- Transfer green onions to a bowl and add soy sauce, rice vinegar, sesame oil, gochugaru, and garlic. Stir well. Refrigerate until serving.
- Add ground beef and 3 tablespoons of Takumi sauce to a medium bowl and combine. Form into 4 large patties.
- Heat a grill pan or outdoor grill to medium-high heat and lightly grease with cooking oil. Grill burgers for 4-5 minutes. Flip burgers and brush with remaining Takumi sauce. Grill 4-5 minutes longer. Rest for 5 minutes before serving.
- Serve burgers on buns with lettuce and topped with pajeori salad.