In a mixing bowl, combine thinly sliced beef sirloin or ribeye with soy sauce and sesame oil. Allow the beef to marinate for 15 minutes at room temperature.

Heat a large pan or wok over medium-high heat and add vegetable oil. Add the marinated beef to the hot oil, quickly stir-frying until browned, about 2-3 minutes. Transfer beef to a plate and set aside.

In the same pan, add more vegetable oil if necessary, and add chopped onion, minced garlic, and grated ginger. Stir-fry for about 2 minutes until fragrant and onions are translucent.

Push the aromatic mixture to one side of the pan, pour in the beaten eggs into the empty space, and scramble for 1-2 minutes until just set. Incorporate the eggs with the onion mixture.

Add the chilled jasmine rice to the pan, breaking apart clumps with your spatula. Stir-fry for about 3 minutes to absorb the flavors.

Pour in the remaining soy sauce and oyster sauce, and add frozen peas and carrots. Continue cooking and stirring for about 2-3 minutes.

Return the seared beef to the pan with sliced green onions and gently fold into the rice. Stir everything for another minute.

Season with salt, pepper, and fish sauce if desired. Transfer the Savory Onion Beef Fried Rice to serving plates, garnish with extra green onions, and serve hot.