Heat vegetable oil in a large skillet or wok over medium-high heat.
Add the mixed vegetables and cook for 3-4 minutes until they are tender.
Push the vegetables to the side and pour the beaten eggs into the skillet.
Scramble the eggs until fully cooked, then mix with the vegetables.
Add the cooked rice to the skillet, breaking up any clumps.
Pour in the soy sauce and sesame oil, stirring well to combine.
Add cooked chicken or shrimp if using, and stir until heated through.
Season with salt and pepper to taste.
Stir in the chopped green onions and remove from heat.
Garnish with fresh cilantro before serving.