In a medium-sized bowl, mix together the flour, garlic salt, onion powder, and pepper, set aside.
In another medium-sized bowl, whisk together the eggs and the water, set aside.
In a large bowl, mix together the breadcrumbs, parmesan cheese, and Italian seasoning.
To set up your breading station, place the chicken cutlets, flour bowl, egg bowl, and breadcrumb bowl next to each other. Then line a sheet pan with parchment paper and keep it nearby.
Place one chicken cutlet into the flour mixture and evenly coat it making sure to shake off any excess flour.
Next, dip the cutlet into the egg mixture to evenly coat it and allow any excess egg mixture to drip off.
Place the cutlet into the breadcrumb mixture and gently press the breadcrumbs in so they stick all over shaking off any excess breadcrumbs.
Place the breaded cutlet onto the prepared sheet pan and repeat with the remaining chicken pieces.
Once all of the chicken is breaded, add about ¼ inch of oil to a large skillet over medium heat. After doing that, preheat the oven to 375 degrees F.
Once the oil is hot, fry the chicken in batches, making sure that they do not touch, for 4-5 minutes per side until golden brown and the internal temperature reaches 165 degrees F. (you can check this with a kitchen thermometer).
Place the chicken on a paper towel-lined plate to soak up any of the excess oil.
Then, place the chicken on a wire rack over a sheet tray while you fry the remaining pieces (this helps the breading from getting soggy).
While you are frying the chicken, cut the hoagie rolls almost all the way in half lengthwise, carefully open them so they don’t split in half, and place them cut side up onto a large sheet pan.
In a small bowl, stir together the butter, parmesan cheese, garlic powder, and Italian seasoning.
Spread the butter evenly inside of the hoagie rolls.
Place in the oven for 3 minutes to lightly toast the bread.
Spread about 2 tablespoons of the warm marinara sauce on both the top and bottom of the bread. Sprinkle half of the cheese on top of the bottom piece of bread.
Add a piece of chicken on top of the cheese and spread another 2 tablespoons of sauce on top of the chicken. Top with the remaining cheese. Gently close the sandwich as best you can.
Take a large piece of aluminum foil and spray it lightly with non-stick cooking spray. Wrap a sandwich with the foil loosely and place it back on the sheet pan, repeat with the remaining sandwiches.
Bake for an additional 12-15 minutes until the cheese is melted and the sandwich is warm throughout. Serve with the extra marinara on the side for dipping if desired.