In a large mixing bowl, combine the buttermilk, garlic powder, onion powder, smoked paprika, dried thyme, a pinch of salt, and freshly ground black pepper. Add the chicken breasts, ensuring they are completely submerged in the marinade. Cover the bowl with plastic wrap and refrigerate for a minimum of 2 hours, or for optimal flavor, overnight.
In a separate bowl, whisk together the all-purpose flour, cornmeal, baking powder, and freshly grated Parmesan cheese. Season this mixture lightly with a bit more salt and freshly cracked black pepper to taste.
Preheat your oven to 375°F (190°C). To facilitate easy cleanup later, line a baking sheet with parchment paper.
Once marinated, remove the chicken breasts from the bowl and allow any excess marinade to drip off. Take each chicken breast and dredge it in the flour mixture, ensuring an even coating on all sides. Gently shake off any excess flour before moving to the next step.
In a large skillet, heat the olive oil over medium heat until shimmering. Carefully add the coated chicken breasts to the skillet and sear for 3-4 minutes on each side, or until they develop a beautiful golden brown crust.
Transfer the seared chicken breasts to the prepared baking sheet. Place the sheet in the preheated oven and bake for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and is juicy and tender.
Once baked, let the chicken breasts rest for 5 minutes before slicing. This resting period helps retain the juices, ensuring a tender bite. Finally, garnish with freshly chopped parsley just before serving for a burst of freshness.