Boil the noodles: Bring a large pot of salted water to a rolling boil.
Cook noodles until just tender with a little bite. Reserve 1/2 cup of the starchy cooking water, then drain.
Prep aromatics: While the noodles cook, mince the garlic and slice the green onions. Grate ginger if using.
Stir the sauce base: In a bowl, whisk sesame paste (or tahini) with soy sauce, rice vinegar, brown sugar or honey, chili oil/crisp, and toasted sesame oil.
Add 2–3 tablespoons of hot noodle water to loosen and create a smooth, glossy sauce.
Bloom the garlic: Heat the neutral oil in a large skillet or wok over medium-low. Add garlic (and ginger if using) and cook 30–45 seconds until fragrant, not browned. Browning can turn it bitter.
Combine: Add the drained noodles to the skillet and toss to coat in the aromatic oil.
Pour in the sesame-chili sauce and toss vigorously. Splash in more noodle water as needed to make it silky and evenly coated.
Taste and adjust: Add more soy for salt, vinegar for brightness, or chili oil for heat. Fold in sliced green onions and sesame seeds.
Finish and serve: Plate the noodles warm or at room temperature.
Top with extra chili crisp, cucumber shreds, or a soft-boiled egg if you like.