Bring a pot of salted water to a boil and cook the noodles according to package instructions. Drain them just before they’re fully soft so they don’t overcook later. Reserve a little pasta water in case you need to loosen the sauce.
Heat sesame oil in a skillet over medium heat. Add the minced garlic and stir constantly until fragrant but not browned. This step creates the aromatic base of the entire dish.
Lower the heat and add soy sauce, brown sugar, rice vinegar, and chili flakes to the skillet. Stir gently until the sugar dissolves and the sauce looks glossy. Keep the heat low to avoid burning.
Add the cooked noodles directly into the skillet. Use tongs to toss everything together so the noodles absorb the sauce evenly. Add a splash of pasta water if needed for smooth coating.
Turn off the heat and sprinkle in green onions and sesame seeds. Give it one final toss and taste for seasoning. Serve immediately while hot and glossy.