Set out 3 large baking sheets. Line one of the pans with parchment paper. Set a wire rack over the second pan. Line the third pan with aluminum foil. Set aside.
On a large, shallow plate, combine the flour, cornstarch, salt, and garlic powder.
On a second shallow plate, add eggs and water. Whisk to combine.
On a third plate, add 1 cup of the flour mixture and parmesan cheese. To this bowl, add the panko. Toss to combine.
One at a time, remove a fillet of chicken from the buttermilk mixture. Dredge it first in the flour mixture, then the egg mixture, and finally the panko mixture. Place on the parchment-lined pan. Repeat with the remaining chicken.
When ready, heat oil in a large skillet over medium heat until the oil reaches a temperature of 350°F.
Add 2-3 pieces of coated chicken (or as many as your skillet can hold) to the pan and cook for 4-5 minutes. Flip and cook the other side for another 4-8 minutes, or until the internal temperature of the chicken reaches 165°F. The chicken should be crispy and golden brown.
Remove the chicken from the oil and place on the wire rack. Repeat with the remaining pieces of chicken.