1.Put the beef and shiitake mushrooms into a bowl and mix with 1 clove of garlic, 1 teaspoon sugar, ¼ teaspoon ground black pepper, 2 teaspoons soy sauce, mirin, cornstarch, and 1 teaspoon of toasted sesame oil. Cover and keep it in the fridge.
2.Crack the egg in a bowl and add a pinch of salt. Beat until well combined. Add 1 teaspoon of vegetable oil to a heated nonstick pan. Swirl the oil around so it covers the pan. Tilt it around so the mixture spreads thinly. Cook for about 1 minute. Flip it over and let it sit on the pan for 1 more minute. Remove to a cutting board and cut into ribbons.
3.Bring a large pot of water to a boil. Add the spinach and blanch for 30 seconds to 1 minute, then take it out and put it in a bowl of cold water. Squeeze it with your hands to remove any excess water. Cut it a few times and put it into a large bowl. Mix with 1 teaspoon soy sauce and 1 teaspoon sesame oil.
4.Put the noodles into the boiling water, cover and cook for 1 minute. Stir them so they don’t stick together. Keep cooking for another 7 minutes until the noodles are soft and chewy. Strain and cut them a few times with kitchen scissors. Put the noodles into the large bowl next to the spinach. Add 2 teaspoons sesame oil, 1 teaspoon soy sauce, and 1 teaspoon sugar. Mix well.
5.Heat up a skillet over medium high heat. Add 2 teaspoons vegetable oil with the onion, the green onion, and a pinch of salt. Stir-fry about 2 minutes until the onion looks a little translucent. Transfer to the noodle bowl.
6.Heat up the skillet again and add 2 teaspoons vegetable oil. Add the white mushrooms and a pinch of salt. Stir-fry for 2 minutes until softened and a little juicy. Transfer to the noodle bowl.
7.Heat up the skillet and add 1 teaspoon vegetable oil. Add the carrot and dash of salt then stir-fry for 1 minute. Add the red bell pepper strips and a dash of salt then stir-fry another minute. Transfer to the noodle bowl.
8.Heat up the skillet and add 2 teaspoons vegetable oil. Add the beef and mushroom mixture and stir fry for a few minutes until the beef is no longer pink and the mushrooms are softened and shiny. Transfer to the noodle bowl.
9.Add 1 minced garlic clove, 1 tablespoon soy sauce, 1 tablespoon sugar, ½ teaspoon ground black pepper, and 2 teaspoons of sesame oil to the mixing bowl full of ingredients. Mix all together by hand. Add the egg garnish and sesame seeds. Mix it and serve immediately.