Boil the noodles: Bring a large pot of salted water to a boil. Cook the noodles according to package directions until just tender. Reserve 1/4 cup of the starchy cooking water before draining.
Prep the aromatics: While the noodles cook, mince the garlic and grate the ginger.
Slice the scallions and set aside some for topping.
Whisk the sauce: In a bowl, combine soy sauce, sesame oil, rice vinegar, honey or sugar, and chili oil/crisp if using. If adding peanut butter or tahini, whisk it in now. Add 2 tablespoons of water or cooking water to help the sauce loosen.
Warm the aromatics: Heat the neutral oil in a large skillet over low heat.
Add garlic (and ginger if using) and stir just until fragrant, about 20–30 seconds. Do not brown.
Toss everything together: Add the cooked noodles to the skillet. Pour in the sauce and toss with tongs until evenly coated, glossy, and hot.
Add a splash more cooking water if the sauce feels tight.
Finish and serve: Stir in most of the scallions. Taste and adjust with more vinegar for brightness, honey for balance, or soy for salt. Plate and top with sesame seeds and the remaining scallions.