Cut the chicken into small, even-sized pieces for uniform cooking. Combine the chicken with the seasoning mix and, if desired, blend in 2 tablespoons of buttermilk or yogurt. Cover and refrigerate for at least 30 minutes or up to 8 hours. Add the egg whites or buttermilk to the marinated chicken and mix thoroughly. Dust in cornstarch gradually, ensuring each piece is well-coated and the mixture remains moist. Spread the panko crumbs on a plate. Working piece by piece, dredge the chicken in the crumbs, pressing gently so the coating adheres firmly, resembling a double-breaded texture. Arrange the breaded pieces on a tray, then allow them to rest for 10–15 minutes or refrigerate in an airtight container for up to 48 hours.

Heat oil in a deep pan over medium heat until it reaches about 350–375°F (175–190°C). Test by dropping a breadcrumb—if it sizzles and rises without burning, the oil is ready. Carefully lower each breaded chicken piece into the oil without stirring immediately to prevent the coating from separating. Avoid overcrowding; fry in batches to maintain the oil’s temperature. After 2 minutes, stir gently and fry until each piece turns golden and crisp, ensuring the internal temperature reaches 165°F (74°C). Transfer the cooked chicken to a wire rack set over paper towels or to a colander. Between batches, lower the heat, skim out loose crumbs with a mesh skimmer, and bring the oil back to frying temperature before proceeding.

Baking Option: Preheat the oven to 375°F (190°C). Arrange the prepared chicken on a tray and bake on the center rack for about 14 minutes, turning halfway through, until fully cooked.

Air Fryer Option: Place the coated chicken in the air fryer basket and cook at 400°F (200°C) for approximately 10 minutes, flipping at the 5-minute mark. Ensure the internal temperature reaches 165°F (74°C) before serving.