In a medium bowl, whisk together soy sauce, chicken broth, brown sugar, rice wine vinegar, cornstarch, sesame oil, fresh ginger, minced garlic and red pepper flakes.
FOR THE STIR FRY
Add chicken pieces to the bowl and stir to coat them with the marinade. Transfer bowl to the refrigerator and allow to marinade for at least 15 minutes.
Heat 1 tablespoon vegetable oil in a large pan over medium heat. Add the carrots and broccoli and cook until tender, about 8 minutes. Then add in asparagus and cook vegetables for an additional 5 minutes. Remove from heat and keep warm while you cook the chicken.
Add 1 tablespoon vegetable oil to a large pan over medium heat. Remove chicken from marinade and reserve liquid.
Add chicken to pan and cook until chicken is cooked through, about 6-7 minutes.
Add in cooked vegetables and uncooked snap peas. Add remaining marinade to skillet and stir until chicken and veggies are coated and marinade begins to boil and thicken. Add in walnuts and stir to incorporate. Serve immediately.