Cook rice and let it cool completely
Heat a pan or wok over medium-high heat
Add oil and let it heat
Add chopped onion, garlic, or other aromatics if desired
Add vegetables and cook until tender
Add protein if using and cook through
Add the cold rice and break up any clumps
Stir-fry the rice until heated evenly
Add soy sauce, salt, pepper, or other seasonings
Push rice aside and scramble an egg if desired, then mix it in
Toss everything together until well combined
Cook for another minute or two
Serve hot