Chop the onions and green onions into bite-sized pieces. If you're using cucumber, slice it into thin matchsticks.

In a non-stick wok or pan, combine the black bean paste with enough vegetable oil, about half the amount of the black bean paste. Heat it over medium heat, stirring continuously until bubbles start to form in the center. Once ready, turn off the heat and transfer it to an airtight container.

In another wok, heat 3 tablespoons of cooking oil, which can be the oil used for frying the black bean paste. Once the oil is hot but not burning, add the minced ginger and soy sauce to sauté, being cautious of any oil splatter. Stir in half of the green onions and sauté until fragrant.

Add the remaining green onions, white onions and soy sauce (watch out for oil splatter), then stir-fry over high heat. Then, mix in the sugar, oyster sauce, veggie stock (or bouillon powder), and the fried black bean paste.

Pour in 200 ml of water and let the mixture simmer for more than 5 minutes.

While the sauce simmers, prepare the slurry by mixing the potato or corn starch with water in a small bowl. Once the sauce has simmered, add the slurry and stir immediately until the sauce thickens. Then add the tofu crumble and make sure it warms through. Keep it covered and warm until you're ready to serve.

Bring a pot of water to a boil and cook the noodles according to the package instructions. If using fresh noodles, rinse them under cold water and drain.

Divide the cooked noodles into serving bowls and top with the sauce. Garnish with cucumber if desired, and serve alongside kimchi or Korean pickled radish. Enjoy!