Bring a pot of water to a boil and cook the noodles until one minute short of al dente. Reserve about ¼ cup of the noodle water, then rinse the noodles under cold water and drain.
In a bowl, combine the peanut butter, light soy sauce, sesame oil, chili crunch, sugar, rice vinegar, reserved noodle water, garlic, and ginger. Whisk until smooth and fully incorporated, adding a splash more noodle water if the sauce is too thick.
Add the noodles to the bowl and toss until the sauce clings to every strand.
Transfer to a bowl and optionally garnish with chili oil and scallions.
