Bring a large pot of salted water to a boil and prep your vegetables by slicing ahead of time.
Marinade and Sauce: In a small bowl whisk the soy sauce, dry sherry, cornstarch, brown sugar, and salt together until the cornstarch is completely dissolved. Slice the chicken breast in half, horizontally, and then slice diagonally into thin strips. Place the strips into the marinade mixture and set aside.
Place the Noodles into the boiling water and cook according to package directions (usually around 5 to 6 minutes), drain, and run cold water over to cool. Set aside as you’re cooking the vegetables.
Vegetables: Heat 1 tablespoon of oil in a wok or large skillet. Add the peas, bell pepper, garlic cloves, and scallions and stir-fry, tossing occasionally, until tender, but still crisp, about 2 to 3 minutes. Remove from wok or skillet and set aside on a plate.
Chicken: Add the remaining 2 tablespoons of oil to the wok or skillet and using kitchen tongs pick the chicken out of the marinade/sauce and place in a SINGLE layer in the wok (or skillet). Keep the marinade/sauce on the side. Let chicken brown for 2 minutes before flipping to the other sides and cooking for an additional 1 to 2 minutes.
Stir-Fry: Add the cooked noodles, vegetables, and leftover marinade/sauce to the wok or skillet. Toss until the sauce evenly coats the stir-fry and cook for 2 more minutes to allow it to thicken. Garnish with sesame seeds.