Remove the noodles from the package and soak in a bowl of hot water to soften while you are preparing everything else. Discard the spice packet that comes with the noodles, you won't be needing it.
Add the soy sauce, cornstarch, rice vinegar, brown sugar, garlic, ginger, chili sauce, and chicken stock in a bowl and whisk to combine. Set the sauce aside.
In a large saucepan or pot over med-high heat, add the oil and chicken to cook through. Once the chicken is fully cooked, remove it from the pan into a small bowl and set aside.
In the same pan, add the broccoli and carrots (or any vegetable you choose) and cook for 2-3 minutes to soften. Add the sauce and the cooked chicken to the pan with vegetables and stir together.
Drain the noodles and add them to the pan. Stir everything to combine and allow to heat back up and cook for another 4-5 minutes.
Remove the pan from the heat and serve in bowls. Sprinkle the top with sesame seeds and green onion. If you are adding the egg, cut it in half and place it on top. Enjoy!