Coat The Chicken. In a medium bowl, combine chicken, cornstarch, salt, and pepper. Stir with a fork to evenly coat the chicken pieces.
Mix Up The Sauce. Next, mix up your sauce. (You can also do this while the chicken cooks to save time!) In a liquid measuring cup or small bowl, combine chicken broth, honey, gluten-free tamari, rice vinegar, garlic, and red pepper flakes. Whisk to combine and set aside.
Cook The Chicken. Heat 1-2 Tablespoons oil in a large skillet over medium heat. Working in batches so you don't overcrowd the pan, cook the chicken 5-6 minutes on the first side, then flip and cook another 3-4 minutes, or until chicken is browned on each side and mostly cooked through (we'll finish cooking it later!). Remove chicken from pan and set aside on a clean plate. Repeat with remaining chicken until all chicken is cooked, adding more oil to the pan, if needed.
Simmer The Sauce. When the chicken is all cooked and set aside, add butter to the pan and stir to scrape up any browned bits from the bottom of the pan. Add sauce to the skillet and bring to a simmer over medium heat. Add chicken back to the pan and simmer another 3-4 minutes, or until the sauce has thickened and the chicken is fully cooked through to 165 degrees F.
Serve & Store. Garnish the chicken with cilantro, green onion, sesame seeds or red pepper flakes and serve warm with rice and broccoli. Store leftover chicken in an airtight container in the fridge 3-4 days.