Heat the toasted sesame oil in a large skillet or wok over medium-high heat.
Add the diced chicken breast to the pan, season with sea salt and black pepper, and sauté until golden and cooked through.
Push the chicken to the outer edges of the pan and add the white onion, garlic, and ginger to the center, cooking until fragrant.
Stir in the peas and carrots and cook for 2-3 minutes until they are tender-crisp.
Add the chilled cooked brown rice to the skillet, breaking up any clumps with a spatula, and stir to combine with the chicken and vegetables.
Push the rice mixture to the side, crack the egg into the empty space, and scramble it until just set before folding it into the rice.
Drizzle the coconut aminos over the entire mixture and toss well to coat, heating everything through for another minute.
Remove from heat, garnish with freshly sliced green onions, and serve immediately.