One at a time, set each breast of the 2 pounds boneless skinless chicken breasts in between two layers of plastic wrap and flatten to 3/4 inch thickness by using a mallet or rolling pin. Soak the flattened chicken in 1 cup buttermilk for at least 30 minutes.
In a shallow dish, combine 1 cup panko bread crumbs, 1 cup finely grated parmesan cheese, 1 teaspoon garlic powder, 1 teaspoon paprika, and 1 teaspoon dried thyme. Shake excess buttermilk off each piece of chicken and coat in the bread mixture.
Lay in a single layer on a parchment lined baking sheet and bake in preheated 400°F oven for about 20 minutes or until the internal temperature reaches 165°F. Feel free to flip half way through cooking to crisp up both sides. Season with salt and pepper, as desired.