Pat the chicken breast dry with paper towels and cut into 1-inch bite-sized pieces.
In a small mixing bowl, whisk together the tamari, honey, rice vinegar, arrowroot powder, minced ginger, minced garlic, and red pepper flakes until smooth.
Heat the avocado oil in a large stainless steel skillet or wok over medium-high heat until it begins to shimmer.
Add the chicken pieces to the hot skillet in a single layer and sear without moving for 2-3 minutes to develop a golden crust.
Flip the chicken and continue cooking for another 3 minutes until fully cooked through, then remove the chicken from the pan and set aside.
Add the broccoli florets to the same pan with two tablespoons of water; cover with a lid for 2 minutes to steam-sauté until they are vibrant green and tender-crisp.
Return the chicken to the pan and pour the prepared sauce over the chicken and broccoli.
Toss everything constantly for 1-2 minutes as the sauce bubbles and thickens into a translucent, sticky glaze.
Remove from the heat and stir in the toasted sesame oil.
Garnish with thinly sliced green onions and sesame seeds before serving hot.