It's the next day right? Good. Heat your wok over medium high heat until it starts to smoke.
Add the oil. Swirl it around the wok. Add the diced chicken and stir fry until the chicken is done. If your pieces are small this should take about a minute. Remove the chicken and set aside.
There should still be a lot of oil in the pan. Add the beaten egg. It should balloon around the edge immediately if you have the heat high enough. Scramble the egg. Try to break it up into little pieces.
Add the crushed garlic and the white part of the green onions. Stir fry for about 20 seconds then add the char siu and continue to stir for about 10-15 seconds to warm it through.
Add the rice, soy, the chicken you cooked and MSG. You can leave the MSG out if you want. Won't be quite the same but do what's right for you.
Turn the heat up to max. Stir fry the rice. That means move it around constantly. By constantly I mean constantly. No breaks. Do somewhere between 3 to 5 minutes. The exact time depends on the wok you choose and the output of your stove.
The rice is done when it is ever so slightly toothy and pretty dry. Like you get at your local Chinese restaurant. Assuming your local Chinese restaurant knows how to fry rice.
Add the finely chopped green part of the green onions and stir to combine. Serve. Feel special.