In a shallow bowl, whisk together the flour, 1 tablespoon garlic powder, Italian seasoning, 1/2 tablespoon kosher salt, and 1/4 tablespoon pepper; set aside.
In a second shallow bowl, whisk the milk with the remaining 1/2 tablespoon garlic powder, remaining kosher salt, and remaining pepper; set aside.
In a third shallow bowl, combine the Panko breadcrumbs and grated Parmesan; set aside.
Pound or press each chicken breast half lightly if uneven, then dredge one piece at a time in the flour mixture, shake off excess, dip in the milk mixture, and press into the breadcrumb mixture to coat thoroughly. Place coated cutlets on a parchment-lined baking sheet and repeat with remaining cutlets.
Heat 2 tablespoons olive oil in a large skillet over medium-high until shimmering. Add cutlets without crowding (work in batches if needed) and cook until golden and releasing easily, about 4–5 minutes per side. Transfer cooked cutlets to a plate and keep warm.
Bring a large pot of water to a boil. Add the chopped broccoli rabe and blanch for 1 minute. Drain and pat dry.
Heat 1 tablespoon olive oil in a skillet over medium heat. Sauté the blanched broccoli rabe 2–3 minutes, seasoning with salt and pepper to taste; set aside.
Stir together the mayonnaise and pesto in a small bowl. Spread the mixture evenly on both cut sides of the ciabatta halves.
Layer provolone slices on the bottom half of the ciabatta, top with the cooked chicken cutlets, then arrange roasted red peppers and sautéed broccoli rabe over the chicken.
Place the top half of the ciabatta over the filling and slice the sandwich into individual pieces about 3 inches wide. Serve immediately.
