Preheat your oven to 350° F.
Filet both pieces of chicken in half lengthwise, resulting in 4 thin slices. Cover with plastic wrap and flatten with a rolling pin until each slice is under half an inch. Sprinkle both sides with 2 teaspoons of garlic powder and store on a paper towel to the side.
Start heating your cast iron skillet over medium-high heat.
Combine breadcrumbs, ½ cup of parmesan cheese, fresh basil, onion powder, and remaining garlic on a large plate and set aside.
In a shallow bowl, whisk water and eggs and set aside. Spread the flour on a plate and set aside.
Coat the chicken in the flour and shake off the excess. Dip in egg mixture and then coat in breadcrumbs, making sure the crumbs adhere and chicken is fully coated.
Add olive oil to the skillet, followed by the chicken slices two at a time and sauté until golden, 2-3 minutes per side. Remove all 4 slices and set on a plate lined with paper or a paper towel.
Add ½ a cup of tomato sauce to the bottom of the cast iron skillet. Sprinkle ½ of shaved parmesan over sauce. Return all four pieces of chicken to the cast iron skillet and arrange with the least amount of overlap possible. Top with remaining shaved parmesan cheese.
Cover with remaining sauce, remaining grated parmesan cheese, and top each piece of chicken with shredded fresh mozzarella cheese. Sprinkle with basil and bake uncovered for 30 minutes.
Serve immediately alone or with a side of pasta if desired.