Combine rice noodles, chicken, bok choy, carrot, green onion, dashi, nutritional yeast, ginger, black pepper, white pepper, and red pepper flakes in a large, portable bowl with a lid.
Combine tamari, sesame oil, and miso paste in a small, portable container. Cover and shake until combined.
Add hot water to the noodle bowl when ready to eat. Push aside the noodles and crack egg into the middle, stirring constantly with chopsticks. Close lid and let sit until noodles soften, about 3 minutes. Remove the cover and pour in tamari mixture.