Prep the rice: If you haven’t already, cook rice the day before.
Spread it on a tray to cool, then refrigerate. Cold, dry rice fries better and won’t clump.
Mix the sauce: In a small bowl, whisk soy sauce, oyster sauce, sesame oil, sugar (if using), and pepper. Set aside.
Season the chicken: Pat the diced chicken dry.
Toss with a pinch of salt and a splash of soy sauce. Dry chicken browns better.
Scramble the eggs: Heat a large skillet or wok over medium heat. Add a few drops of oil, pour in eggs, and scramble until just set.
Remove to a plate.
Cook the chicken: Increase heat to medium-high. Add 1 tsp oil, then chicken. Spread it out and let it sear for 2–3 minutes before stirring.
Cook through and remove to the same plate as the eggs.
Sauté aromatics: Add a bit more oil if needed. Cook onion and the white parts of the green onions for 2–3 minutes until soft. Add garlic and cook 30 seconds until fragrant.
Add veggies: Stir in mixed vegetables.
If using frozen, add them straight from the freezer. Cook 3–4 minutes until hot and slightly crisp.
Fry the rice: Add the chilled rice, breaking up clumps with a spatula. Press it into the pan to get some contact and light browning.
Stir and repeat for 3–5 minutes.
Combine and sauce: Return chicken and eggs to the pan. Pour in the sauce and toss until everything is evenly coated. Taste and adjust with more soy sauce, pepper, or a pinch of salt.
Finish: Stir in the green onion tops.
Add red pepper flakes or a drizzle of sriracha if you like heat. Remove from heat and let it steam for 1 minute.
Portion: Divide into 4–6 airtight containers. Let cool uncovered for 10–15 minutes before sealing to prevent condensation.