Preheat your Blackstone griddle to medium-high heat and let it get fully hot before adding anything. Drizzle 1 tablespoon vegetable oil over the surface and spread it out evenly. Add the diced chicken in a single layer. Season with salt and pepper and let it cook undisturbed for 2–3 minutes to get a nice sear. Stir and continue cooking for about 5–7 minutes until fully cooked and lightly golden. Move the chicken to one side of the griddle. Drizzle a little more oil onto another section of the griddle. Pour in the beaten eggs and scramble them quickly using your spatula. Once just set, move the eggs next to the chicken. Add butter to the center of the griddle. Once melted, add diced onions and cook for 2–3 minutes until soft and slightly golden. Stir in the minced garlic and cook for about 30 seconds until fragrant.
Add the frozen peas and carrots directly onto the griddle and cook for 2–3 minutes until heated through. Keep everything moving so nothing burns.
Add the cold rice to the center of the griddle. Break it up with your spatula so there are no clumps. Drizzle sesame oil over the rice and spread it out into an even layer. Let it cook for a couple of minutes so it starts to crisp slightly on the bottom.
Toss the rice and continue stir-frying for about 4–5 minutes, pressing it down occasionally to get that classic hibachi-style texture.
Add the cooked chicken, scrambled eggs, and vegetables back into the rice. Pour soy sauce evenly over everything and toss well so the rice is fully coated and evenly seasoned.
Taste and adjust with salt and pepper if needed. Keep stirring for another 1–2 minutes until everything is hot and well combined.
Remove from heat, sprinkle sliced green onions on top, and serve immediately while hot.