Prepare all vegetables by finely chopping the onion, slicing green onions and separating the white and green parts, mincing the garlic, grating the ginger, and cutting the cucumber into thin matchsticks for garnish.
2
Combine the Korean chili pepper flakes, sugar, soy sauce, oyster sauce, and mirin in a bowl and mix well.
3
Bring a pot of water to a boil, add the noodles, and cook according to package instructions. Drain and set aside.
4
Heat oil in a large wok or pan over medium-high heat, add the ground beef in an even layer, season with salt, sear for about 2 minutes until golden, then break it up and stir-fry for 1-2 minutes until fully browned.
5
Add the onion, white parts of the green onions, garlic, and ginger to the beef and stir-fry for about 1 minute until fragrant.
6
Add the cooked noodles to the beef and aromatics, and stir-fry for about 1 minute to coat everything evenly.
7
Pour in the prepared sauce and stir-fry for about 2 minutes until everything is well combined, then turn off the heat.
8
Add the sesame oil and give everything a final toss until well combined.
9
Plate the noodles and garnish with cucumber matchsticks and green onion tops. Add chili crisp on top if desired for extra heat and flavor.