Mix together in a small bowl the soy sauce, brown sugar, hoisin sauce, mirin, ¼ c of water and black pepper. In another small bowl or ramekin, mix together the 2 tbsp of water and cornstarch, this is our cornstarch slurry to thicken the sauce. Set aside.
Bring a pot of water to a boil and cook the noodles according to the package directions.
While the water is coming to a boil and the noodles are cooking, start preparing the beef.
Heat a wok or skillet over medium high heat. Add in the ground beef and brown the beef until you don't see any more pink, drain and set the ground beef aside.
To the same wok over medium heat, add in the oil. Once hot add in the white part of the green onion, garlic, red pepper flakes and ginger. Stir for 30 seconds.
Next add in the soy sauce mixture and cornstarch slurry. You might need to whisk together the cornstarch slurry once more before adding. Then, add in the ground beef, let cook for about 4 minutes, stirring occasionally.
Lastly add in the noodles, the green part of the green onion and sesame oil. Toss everything together. Serve, eat and enjoy!