Heat the sesame oil in a large skillet or wok over medium-high heat until shimmering.
Dice the chicken breast into bite-sized pieces and season with sea salt and black pepper.
Add the chicken to the skillet and sear until golden brown and cooked through, then remove from the pan and set aside.
In the same skillet, add the minced garlic and grated ginger, sautéing for 30 seconds until fragrant.
Add the frozen peas and carrots along with the cauliflower rice, stir-frying for 3-4 minutes until the vegetables are tender-crisp.
Push the vegetables to the side of the pan and pour in the whisked egg, scrambling it quickly until just set.
Return the cooked chicken to the pan along with the chilled brown rice and tamari.
Toss all ingredients together for 2 minutes over high heat until the rice is slightly toasted and everything is well-combined.
Garnish with sliced green onions and serve immediately.