Boil water for noodles.
Make seasoning sauce.
Marinate beef with 2 TBS of the seasoning. (If you are omitting beef, remove 2 TBS of seasoning for future use.)
Lightly sauté onion, carrot with vegetable oil on high heat. Add a little bit of salt and pepper.
Sauté spinach with a little water and a touch of salt and pepper on high heat until wilted.(More traditional way is to blanch spinach in boiling water with salt, wash in cold water, squeeze out water and then season with salt, pepper and garlic but I find this method way too time consuming to make a big difference in the overall taste) Mix mushroom with 2 TBS seasoning.
Cook mushroom and beef on high heat.
Boil noodles according to the instructions on the packaging. Rinse in cold water thoroughly and drain. Cut noodles with scissors once or twice (Cutting is optional. Do NOT overcut.)
Coat a preheated pan with vegetable oil, add the noodles and remainder of the seasoning. Mix well and cook for a few minutes.
Add back all vegetables and meat. Mix well.
Taste add salt, pepper and sugar as needed. For extra shine, you can add more sesame oil.
Garnish with sesame seeds. (optional)