Dice the chicken breast into bite-sized pieces and season 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 skillet and sauté until golden brown and cooked through, then remove and set aside.
In the same skillet, add the toasted sesame oil along with the diced white onion, minced garlic, and grated ginger.
Sauté the aromatics for 2 minutes until fragrant, then stir in the frozen peas and carrots.
Add the chilled cooked brown rice to the skillet, breaking up any clumps with a spatula, and pour the tamari over the top.
Push the rice and vegetable mixture to the sides of the pan to create a well in the center.
Crack the egg into the well and scramble it quickly until set, then fold it into the rice mixture.
Return the cooked chicken to the pan and toss everything together for 1-2 minutes to heat through.
Garnish with sliced green onions and serve immediately.