Rinse the rice under cold water in a colander until the water runs clear, about 2–3 rinses.
Place the rinsed rice, 2 cups water, and 1/2 teaspoon kosher salt into the Instant Pot inner pot. Secure and seal the lid.
Cook on Manual/High Pressure for 4 minutes, then allow a 10-minute natural release before venting the remaining steam and opening the lid.
Fluff the cooked rice with a fork and transfer it to a bowl. Rinse and dry the inner pot to remove any stuck rice, then return the pot to the cooker.
Set the Instant Pot to Sauté and heat 3 tablespoons vegetable oil. Add the chicken and chopped onion, season with kosher salt and pepper, and sauté until the chicken is cooked through, about 6–10 minutes.
Add the minced garlic and cook for about 30 seconds, then stir in the frozen peas and carrots and cook for 2 more minutes.
Push the chicken and vegetables to one side of the pot. Pour the beaten eggs into the empty side and gently scramble until softly set, about 1–2 minutes, then fold the eggs into the chicken and vegetables.
Press Cancel. Add the fluffed rice, 1 1/2 tablespoons soy sauce, sliced green onions, and 1 teaspoon toasted sesame oil. Stir until evenly combined and season to taste.
Serve warm, garnished with sesame seeds.