In a small bowl, whisk together the gochujang, tamari, grated ginger, and minced garlic to create a smooth, spicy glaze.
Season the cubed chicken breast evenly with sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the chicken to the pan and sear until golden brown and cooked through, approximately 6 to 8 minutes.
Remove the chicken from the pan and set aside; add the toasted sesame oil to the same pan.
Toss in the broccoli florets and sliced bell peppers, stir-frying for 3 to 4 minutes until they are tender yet still crisp.
Return the cooked chicken to the pan and pour the prepared gochujang sauce over the mixture.
Toss everything together for 1 to 2 minutes until the sauce thickens and creates a glossy coating on the chicken and vegetables.
Serve the stir-fry over the warm brown rice and garnish with sliced green onions and sesame seeds for a final crunch.