Cut the chicken breast into small, bite-sized cubes and season evenly with the sea salt and black pepper.
Heat the sesame oil in a large non-stick skillet or wok over medium-high heat until it begins to shimmer.
Add the chicken to the pan in a single layer and sear without moving for 3 minutes to develop a golden crust, then toss and cook for 2 more minutes.
Add the diced carrots, grated ginger, and minced garlic to the pan, sautéing for 2-3 minutes until the vegetables soften and become fragrant.
Push the chicken and vegetable mixture to the outer edges of the pan and crack the egg into the center, scrambling it quickly until just set.
Incorporate the chilled brown rice and frozen peas into the pan, stirring everything together to combine.
Drizzle the tamari over the rice and press the mixture down firmly with a spatula, letting it sear undisturbed for 2 minutes to create crispy bits.
Toss the fried rice one final time, garnish with thinly sliced green onions, and serve hot.