Cut the vegetables (onion, carrot, cabbage, etc.) and meat into bite-sized pieces.
Blanch the udon noodles in boiling water for 30 seconds, then drain.
Add cooking oil to a pan and stir-fry the meat first.
When the meat is cooked, add the vegetables and stir-fry together.
Once the vegetables are somewhat cooked, add the udon noodles.
Season with soy sauce, oyster sauce, salt, and pepper.
Stir-fry until all ingredients are well combined.
Serve on a plate, and sprinkle sesame oil or sesame seeds if desired.