Prep: Heat oven to 400°F. Lightly grease a 9x13 inch casserole dish.
Flatten: Place chicken between two pieces of plastic wrap. Using a rolling pin or the flat side of a mallet, pound chicken to about 0.5 - 0.75 inch thickness. Rub olive oil all over flattened chicken breasts.
Season: Combine all remaining ingredients except butter in a small bowl. Sprinkle all over chicken, then lightly rub it in.
Bake: Place seasoned chicken in prepared casserole dish. Top each chicken breast with a slice of butter. Bake at 400°F until internal temperature reaches 165°F, about 18-20 minutes. Finish chicken under broiler for 1-3 minutes, until nicely browned. Serve immediately.
Notes
For extra flavor, garnish with fresh herbs like parsley or thyme before serving.