If using freshly cooked rice, spread it out on a baking sheet and let it cool to help dry it out. Day-old rice works best as it’s less sticky.
Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the diced onion to the skillet and sauté for 2-3 minutes until translucent. Add minced garlic and cook for another 30 seconds until fragrant.
Incorporate the mixed vegetables, and stir-fry for about 3-4 minutes until they are tender.
Push the vegetable mixture to one side of the skillet, and pour in the beaten eggs on the other side. Scramble the eggs until fully cooked, then mix them into the vegetable mixture.
Add the cooked rice to the skillet, breaking up any clumps. Stir-fry for 3-4 minutes, ensuring the rice is heated through.
Pour the soy sauce and sesame oil over the rice, along with the black pepper. Mix well to evenly distribute the sauce and flavors.
If using additional protein, add it to the fried rice now, and stir until heated through.
Remove from heat and garnish with chopped green onions before serving.
For extra flavor, consider adding chili flakes or a dash of hot sauce if you like it spicy.