Heat the sesame oil in a frying pan over high heat. Add the pork (or beef) and stir-fry until the meat changes color. Add the kimchi and stir-fry together.

Add the udon noodles and stir-fry for 1–2 minutes, breaking them apart as you cook.

Add the sake, soy sauce, and sugar in order. Finally, add the garlic chives (or leek) cut into 1-inch (about 3 cm) pieces, and quickly stir-fry until just combined. Done!
*You can tear the garlic chives by hand if you prefer.