Place the chicken breasts between sheets of plastic wrap or parchment and pound them to an even thickness of about 1/2 inch. Pat both sides dry with paper towels so the coating has a dry surface to cling to.

Mix the flour, kosher salt, paprika, garlic powder, onion powder, and black pepper in a shallow dish. In a second shallow dish, whisk the eggs with the milk or water until smooth.

For the basic coating, dip each chicken breast in the seasoned flour, then the egg mixture, and again in the flour. For extra crunch, coat it with panko breadcrumbs after the egg mixture instead of making the final flour coating.

Arrange the coated chicken on a plate and let it stand for 5 minutes. This short rest helps the coating adhere during frying rather than sliding away in the pan.

Heat 1/3 to 1/2 cup neutral oil in a large heavy skillet over medium to medium-high heat until it shimmers but does not smoke. Add the butter if using, allowing it to melt without browning too deeply.

Place the chicken in the skillet without crowding it and cook for about 5 to 7 minutes per side, turning once. Continue until the coating is deeply golden and the thickest part of each breast reaches 165°F (74°C).

Transfer the chicken to a wire rack or a paper towel-lined plate and rest for about 5 minutes before serving. A wire rack is best because air can circulate underneath, helping the crust stay crisp.