Prep your ingredients. Have the rice, chicken, vegetables, and sauce ready before you turn on the stove. Fried rice moves fast, so this makes the cooking easier and keeps you from overcooking anything.
Cook the vegetables. Heat the oil in a large skillet or wok over medium-high heat.
Add the onion, garlic, and carrots, then cook for 2 to 3 minutes until they start to soften.
Add the chicken. Stir in the cooked chicken and let it heat through. If your chicken is plain, this step helps it soak up the flavor before the rice goes in.
Scramble the eggs. Push the chicken and vegetables to one side of the pan. Crack the eggs into the empty space and scramble them gently until just set.
Add the rice. Break up the rice with your hands or a spoon before adding it to the pan.
Stir well so the rice mixes with the eggs, chicken, and vegetables.
Season with sauce. Add the Buldak sauce, soy sauce, butter, and sesame oil. Stir until the rice is evenly coated and looks glossy and spicy.
Finish and taste. Cook for another 2 to 3 minutes, stirring often, until everything is hot and slightly crisp in spots. Taste and add salt, pepper, or more sauce if needed.
Top and serve. Turn off the heat and finish with green onions and sesame seeds.
Serve right away while it is hot and flavorful.