Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
If using whole chicken breasts, slice them horizontally into 6 thin, even cutlets. For more even cooking, gently pound any thicker pieces to an even thickness.
In a medium bowl, combine the Greek yogurt and 1 tablespoon Italian seasoning. Add the chicken and toss until each piece is evenly coated. Set aside while you prepare the breadcrumb mixture.
In a separate bowl, combine the panko breadcrumbs, Parmesan cheese, melted butter, remaining 1 tablespoon Italian seasoning, and garlic powder. Mix until the breadcrumbs are evenly coated with the butter and seasonings.
Arrange the chicken cutlets in a single layer on the prepared baking sheet, allowing any excess Greek yogurt mixture to drip off before placing them on the pan.
Spoon the panko mixture evenly over the top of each chicken cutlet, gently pressing it down so the crumbs adhere.
Bake for 18–20 minutes, depending on the thickness of the chicken, until the breadcrumb topping is golden and the thickest part of the chicken reaches an internal temperature of 165°F.