Marinate the Chicken: In a large bowl, combine the buttermilk, Dijon mustard, garlic powder, smoked paprika, onion powder, cayenne pepper, salt, and pepper. Add the chicken breasts and ensure they are fully submerged. Cover and marinate in the refrigerator for at least 2 hours or overnight for best results.
Prepare the Breading: Preheat your oven to 375°F (190°C). In a shallow dish, combine the flour, salt, and pepper. In another dish, place the breadcrumbs.
Bread the Chicken: Remove the chicken from the marinade and let the excess drip off. First, coat each chicken breast in the flour, then dip it back into the buttermilk, and finally, press it into the breadcrumbs, ensuring an even coating.
Bake the Chicken: Place the breaded chicken breasts on a baking sheet lined with parchment paper. Drizzle the melted butter evenly over the chicken. Bake in the preheated oven for 25-30 minutes, or until the chicken is cooked through (internal temperature should reach 165°F or 75°C) and the coating is golden brown.
Rest and Serve: Remove the chicken from the oven and let it rest for 5 minutes. This allows the juices to redistribute, ensuring a moist and tender bite.
Garnish: Sprinkle fresh parsley over the chicken for a pop of color and freshness before serving.