Make bonito powder: Place 0.2 ounces bonito flakes in a small microwavable bowl and microwave them for 1 minute until they become dry. Rub them with your hands to turn them into powder. Set aside.
Make scallions and sesame mix: Place ¼ cup toasted white sesame seeds in a food processor and pulse until they turn into ground sesame. Add ⅓ cup minced scallions and mix together. Set aside.
Make the sauce: Mix 2 tablespoons oyster sauce, 1.5 tablespoons rice vinegar, 1 tablespoon sesame oil, 2.5 teaspoons soy sauce, and ½ teaspoon sugar together and divide them into serving bowls. Add 1 teaspoon of bonito powder to each serving bowl and mix well (you can use the leftover bonito powder as a topping). Set aside.
Prepare other toppings: Prepare any toppings you’d like to use at this point.
Boil noodles: Boil water in a large pot and cook 2 bundles Chinese noodles according to the instructions on the package. Once done, drain them in a strainer.
Assemble the bowl: Divide the noodles into serving bowls over the sauce, and top with your desired toppings. Eat while it’s hot! (note 4)