Add 1 inch of frying oil to a deep skillet. Preheat on the stovetop over medium-high heat. The oil is ready once it sizzles when you sprinkle a breadcrumb or two into the skillet, approx. 350-375 degrees F.

If using chicken breasts, butterfly each piece by slicing in half horizontally, then pound to ½-inch thickness with a meat mallet. If using chicken thighs, lay the thighs flat and make a shallow cut halfway through any extra-thick areas then open like a book to create an even thickness. Season both sides of the chicken with garlic powder, 1 ½ teaspoons kosher salt, and ground black pepper to taste. Set aside while you prepare the breading station.

Set up 3 shallow bowls or containers: one with rice flour, one with beaten eggs, and one with panko breadcrumbs. Season each with a pinch of kosher salt, garlic powder, and ground black pepper. Stir to combine.

Working one piece at a time, lightly coat the chicken in flour, shaking off excess. Dip into the beaten eggs, letting the excess drip off, then press into the panko breadcrumbs, ensuring an even coating. Shake off any excess breadcrumbs and set aside on a clean plate. Repeat with the remaining chicken.

Once the oil is hot, carefully lower the breaded chicken into the skillet, working in batches to avoid overcrowding the pan. Fry for 3-4 minutes per side, or until the panko coating is golden brown and the chicken is cooked through. Transfer the fried chicken to a paper towel-lined plate to drain excess oil. While still warm, season with a pinch of salt. Repeat with the remaining chicken cutlets.

Serve the chicken katsu immediately with katsu sauce and your favorite side dishes.