In a bowl, marinate the beef slices with the soy sauce, sake or wine, corn starch, sesame oil, and white pepper. Set aside while you prep the onion and green pepper.
Rinse the noodles well with hot water and drain. In a wok, or large skillet, heat up the oil over medium high heat. When hot, add the noodles in a thin, even layer. The goal is to fry the noodles into a giant crispy noodle cake. If needed, do this is batches. When the underside of the noodles are golden brown and crispy, flip and continue to crisp, adding oil as needed. When the noodle cake is crisp, remove from the wok/pan and move to your serving dish.
Add a touch of oil to the wok and add the steak, cooking on high. Let brown and sear, tossing as needed. Remove from the pan, or push to the side of the wok, away from the intense heat of the bottom. Add the onions and green peppers on high heat, tossing often, until the onions are translucent, but not brown.
Add the black bean and oyster sauce, as well as the water. Bring to a simmer over medium to high heat. Slowly drizzle in the cornstarch whisked with water. Bring to a simmer to thicken the sauce, stirring often. Taste and adjust seasonings. Scoop the sauce onto the noodle cake and serve immediately, being sure to get both crispy noodles and sauce into your bowl!
