In a large wok or pot, heat the sesame oil over medium heat. Add the cabbage and onions and cook for 4–6 minutes, stirring occasionally, until onions are translucent and cabbage is lightly browned.
2 cups green cabbage, ¼ cup sesame oil, 2 cups yellow onions
Add the pork belly, garlic, and ginger. Cook for 3–5 minutes, stirring, until the pork is no longer pink.
8 ounces boneless, 1 tablespoon garlic, 1 tablespoon fresh ginger
Make a well in the center of the pan. Add the black bean paste and cook it in the oil for 1 minute. Stir everything together until well coated.
¼ cup Korean black bean paste
Add sugar, oyster sauce, and soy sauce. Stir well to combine and let it cook for 2–3 more minutes until glossy.
1 tablespoon sugar, 1 tablespoon oyster sauce, 1 tablespoon soy sauce
In a small bowl, mix ¼ cup water with the cornstarch. Slowly pour this into the pan, stirring constantly. Let it simmer for 2–3 minutes until thickened like gravy. Remove from heat.
½ cup water, 2 tablespoons cornstarch
Cook the noodles according to the package instructions. Drain, rinse briefly under cold water, and fold it into the pan. Toss until the noodles are coated with the sauce.
7 ounces fresh udon noodles
Garnish with julienned cucumber and sliced scallions.
1 cup Persian cucumber, 1 cup scallions