Dice the chicken breast into small, bite-sized pieces and season with sea salt and black pepper.
Heat the avocado oil in a large non-stick skillet or wok over medium-high heat.
Add the chicken to the skillet and sauté until golden brown and cooked through, about 5-6 minutes, then remove and set aside.
In the same skillet, add the minced garlic and ginger, sautéing for 30 seconds until fragrant.
Add the frozen peas and carrots, cooking for 2 minutes until softened.
Push the vegetables to the side, crack the egg into the center, and scramble until just set.
Add the chilled brown rice and cooked chicken back into the skillet, breaking up any clumps of rice with a spatula.
Pour the tamari and sesame oil over the mixture and stir-fry for 3-4 minutes, pressing the rice down occasionally to achieve a slight crisp.
Garnish with thinly sliced green onions and serve immediately.