In a bowl, soak the chicken breasts in buttermilk for at least 1 hour (or overnight) to tenderize and infuse flavor.
In a shallow dish, whisk together the flour, grated Parmesan cheese, garlic powder, onion powder, paprika, salt, and pepper. In another bowl, beat the eggs until well combined. In a third dish, place the breadcrumbs.
Remove the chicken from the buttermilk, allowing excess to drip off. Dip each breast in the flour mixture, coating evenly, then in the beaten eggs, and finally in the breadcrumbs, pressing gently to adhere.
In a large skillet, heat the olive oil over medium heat until shimmering.
Add the breaded chicken breasts to the skillet, cooking for about 5-6 minutes on each side, or until golden brown and the internal temperature reaches 165°F (75°C). Work in batches if necessary to avoid overcrowding the pan.
Once cooked, remove the chicken from the skillet and place it on a paper towel-lined plate to drain excess oil.
Serve the Parmesan chicken hot with marinara sauce drizzled over the top if desired, and garnish with fresh parsley.