In a medium bowl, season the diced chicken with a pinch of salt and pepper. Set aside.
In a large skillet or wok, heat 1 tablespoon of vegetable oil over medium-high heat. Add the diced chicken and cook until golden and crispy, about 5-7 minutes. Remove from the pan and set aside.
In the same pan, add another tablespoon of vegetable oil. Add the minced garlic and chopped onion, sautéing until fragrant and the onions become translucent, about 2-3 minutes.
Toss in the mixed vegetables and stir-fry for an additional 3-4 minutes until they are heated through.
Push the veggies to one side of the pan, add the remaining tablespoon of vegetable oil if needed, and then add the day-old rice. Break up any clumps and stir-fry, letting the rice get crispy, about 5 minutes.
Add the cooked chicken back into the pan, then stir in the soy sauce and oyster sauce (if using). Mix well, ensuring the rice is evenly coated with sauces.
Push the fried rice to one side, add the beaten eggs to the open space, and scramble until fully cooked. Once done, mix them into the rice.
Drizzle sesame oil over the fried rice, adjust seasoning with salt and pepper to taste, and give it one last stir.
Serve hot, garnished with sliced green onions on top.
Notes
Using day-old rice helps achieve the best texture.