Rub the pork with oil, spices and salt and pepper. If using sous vide, place in bag and heat water to 150 degrees. Sous vide for 2-4 hours. Remove from bag and dry and place on a foil lined baking sheet to finish. Heat the broiler, coat the pork in the char siu sauce, and broil until is it browning. Cool slightly and slice.
If using the oven, preheat to 400. Place pork on a foil lined baking sheet and bake for 25-30 minutes until internal temp is 150. Don't overbake. Time will depend on the size and thickness of the meat. If you are glazing, add the char siu sauce to cover and broil as above. If not, broil the tenderloin lightly without the glaze. Cool and slice.
Cook the noodles according to the package (if your package is in korean, this is usually adding to boiling water for about 6 minutes), then drain and rinse under cool water to stop cooking and sticking. Add the tbsp of sesame oil and toss to prevent sticking.
Mix the sauce ingredients together well. Heat your wok or skillet over high heat. Add a tbsp of oil and add the mushrooms and ginger. Cook until browning, tossing them occasionally, and then move to a plate. Add another tbsp of oil and add the cabbage. Allow to blacken in places without moving and then toss it. Add the noodles, sauce, mushrooms and pork and allow to simmer over medium heat, while tossing occasionally. Once the sauce has reduced and coated the noodles, you are ready to serve.