Bring a large pot of water to a full boil, then remove it from heat.
Add the rice vermicelli, fully submerge, and soak for about 10 minutes until just tender.
Prepare the Chicken
Remove the rotisserie chicken from the bag and strip off all the meat, discarding the skin.
Shred the chicken into bite-size pieces and return it to the bag with the reserved juices.
Bloom the Green Onions
Heat a skillet over medium-high heat and add the butter, sesame oil, and green onion whites.
Stir and let everything warm and bloom for about 1 minute.
Add Noodles and Toss
Add mayo, soy sauce, chili crisp, gochujang, brown sugar, rice vinegar, and green onion greens directly into the chicken bag.
Drain the vermicelli well and add it to the bag.
Toss and gently massage the bag until the noodles are fully coated and evenly mixed with the chicken and sauce.
Top with extra chili crisp if desired and serve.
Notes
Soaking vermicelli off heat prevents overcooking and keeps the texture springy.
Mixing directly in the bag captures the rotisserie juices and intensifies flavor without extra dishes.
Letting the noodles rest for a few minutes before serving helps the sauce fully absorb and cling.
If you prefer stronger flavors and seasonings, multiply the portions of seasonings listed above to your preference, but try keep the same proportions for a balanced flavor.