Korean kimchi invigorates a standby weeknight dinner. Bring the pasta water to a boil while you make the meatballs.
1. In a bowl, mix 2 tbsp. soy sauce, 1 tbsp. each vinegar and sesame oil, 1/4 cup green onions, and the bread crumbs and ground beef. Finely chop 1/4 cup kimchi and add to beef mixture. With wet hands, form meatballs the size of ping-pong balls.
2. Heat vegetable oil in a large nonstick frying pan over medium-high heat. Add meatballs and cook, turning, until well browned and cooked through, about 12 minutes. Lift meatballs to a rimmed baking pan, cover with foil, and keep warm.
3. Meanwhile, combine remaining 1 tbsp. soy sauce, 2 tbsp. each vinegar and sesame oil, and 1/4 cup each green onions and kimchi juice. Stir in chili garlic sauce.
4. Cook noodles according to package instructions, drain, and return to warm pot. Toss noodles with sauce and remaining 1 cup kimchi.
5. Divide noodles among 4 bowls, top with meatballs, and sprinkle with remaining 1/4 cup green onions and the sesame seeds.