Bring 2 cups water and vegetable broth to a boil in a large stockpot. Reduce to simmer and add chicken, cooking for 10 minutes.
Add fettuccine, garlic, bell pepper, carrot, sugar, sriracha sauce, soy sauce, sesame oil, rice wine vinegar, red pepper flake, and onion powder to pot. Bring to boil and stir occasionally for 8-9 minutes.
Add peas and cook for 1 minute.
Strain any excess liquid and top with green onion.
Recipe by Rachel Schultz at https://rachelschultz.com/2015/08/11/one-pot-chicken-lo-mein/