Prepare the rice mixture: In a large mixing bowl, combine the chilled rice with soy sauce, sesame oil, garlic powder, and black pepper. Mix thoroughly so every grain of rice is evenly coated with the seasoning. Add the diced vegetables and cooked protein if using. Stir gently to distribute the ingredients without mashing the rice.

Form the rice balls: Take a small handful of the rice mixture (about 2 tablespoons) and flatten it slightly in your palm. If you want a cheesy surprise, place a small cube of shredded cheese in the center, then carefully mold the rice around it, rolling it into a compact ball. Repeat this process until all the rice mixture is used.

Coat the rice balls: Set up a breading station with one shallow bowl of beaten eggs and another of panko breadcrumbs. Roll each rice ball first in the egg, ensuring it’s fully coated, then roll it in the panko breadcrumbs until it’s evenly covered. For extra crispiness, press the breadcrumbs lightly into the rice ball so they adhere well.

Preheat the air fryer: Set your air fryer to 390°F (200°C) and let it preheat for 3–5 minutes. Lightly spray the air fryer basket with cooking spray or brush with a small amount of oil to prevent sticking.

Cook the rice balls: Arrange the rice balls in a single layer in the air fryer basket, leaving space between each for hot air circulation. Lightly spray the tops of the rice balls with cooking spray to help them crisp. Cook for 12–15 minutes, flipping halfway through, until the exterior is golden brown and crunchy. If needed, cook a few extra minutes for an extra crispy crust.

Serve and enjoy: Carefully remove the rice balls from the air fryer and place them on a serving platter. They’re perfect as a snack, appetizer, or party finger food. Serve warm, optionally with a dipping sauce like sweet chili, soy sauce, or spicy mayo for added flavor.