Cook the noodles according to package directions.
In the meantime, cut the spring onions into fine wedges and sauté them in a pan in the neutral oil over medium heat for 3-4 minutes.
For the sauce, combine the following in a small bowl: tahini, chili, 5 spices, sugar, sesame oil, rice vinegar, and soy sauce. Add 6 tablespoons of warm water (the cooking water from the noodles is perfect) and stir everything into a smooth sauce.
Add the sauce to the spring onions in the pan and bring to a boil.
Finally, add the udon noodles to the sauce and mix well. You can also pre-cook the noodles and add them to the sauce while they are cold, then leave the pan on the stovetop until the noodles have warmed up in the sauce.
Sprinkle each serving with a teaspoon of sesame seeds and serve!
