Bring a pot of salted water to a boil and cook noodles according to package instructions, undercooking by about 30 seconds. Save pasta water, then drain and rinse noodles under cold water.
In a cold pan, add peanut butter, chili flakes, green onion, sesame seeds, garlic, sugar, 1 tbsp chili crisp, rice vinegar, and dark soy sauce.
Heat ⅓ cup neutral oil until very hot, then carefully pour it over the cold ingredients in the pan. Stir everything together.
Toss in the noodles and coat them in the sauce. For extra silky noodles, turn heat to medium-low, add 2-3 tbsp reserved noodle water, and mix thoroughly.
Turn off heat, top with more green onion, extra chili crisp, and lime wedges.
