1. Gather all necessary ingredients, including chicken, vegetables, and stir-fry sauce components.
2. Dice boneless, skinless chicken breasts or thighs into 1-inch cubes and pat them dry with a paper towel.
3. Wash and prepare the vegetables, slicing them into even-sized pieces for uniform cooking.
4. Whisk together the stir-fry sauce ingredients in a small bowl until smooth and lump-free.
5. Heat a large skillet or wok over medium-high heat and add 1 tablespoon of cooking oil.
6. Sauté the chicken pieces in a single layer for 4-5 minutes until browned and almost cooked through, then set aside.
7. Add another tablespoon of oil to the skillet, if needed, and stir-fry firmer vegetables, such as broccoli and carrots, for 2-3 minutes.
8. Add softer vegetables, like bell peppers, onions, and mushrooms, and continue to stir-fry until all vegetables are crisp-tender and brightly colored, around 5-6 minutes.
9. Return the cooked chicken to the skillet and pour in the prepared stir-fry sauce.
10. Toss the chicken and vegetables with the sauce to coat them evenly.
11. Let the mixture cook for 2-3 minutes, allowing the sauce to thicken. Stir frequently to prevent sticking.
12. Taste the stir-fry and adjust the seasoning as needed, adding salt, soy sauce, or sriracha if desired.
13. Remove the skillet from the heat and garnish the stir-fry with green onions, sesame seeds, cashews, or red pepper flakes, as preferred.
14. Serve the stir-fry immediately over cooked rice, cauliflower rice, quinoa, or noodles.