Heat oil in a large wok or skillet over medium heat. Add chopped garlic and sauté until golden and fragrant.
Toss in the onion and carrot. Stir-fry for 1–2 minutes, until the onion softens and the carrot is slightly tender.
Add cold, cooked rice. Break apart any clumps and stir to combine well with the aromatics.
Push the rice to one side of the pan. Crack the egg into the empty space.
Let the egg cook for a few seconds, then scramble and mix it evenly into the rice.
Season with oyster sauce, light soy sauce, and pork bouillon powder. Stir-fry until everything is evenly coated and lightly browned.
Add the sliced char siu. Stir-fry briefly to heat through.
Add chopped green onions. Give everything a final toss and serve hot.