Make the Peanut Butter Filling by mixing together the creamy peanut butter and powdered sugar until fully combined. Roll into 12 tablespoon-sized balls and set aside.
Prepare Dry Ingredients by whisking together the all-purpose flour, cocoa powder, baking soda, and salt in another bowl.
Cream Butter and Sugars by beating together the room temperature butter, brown sugar, and granulated sugar until creamy. Mix in the egg and vanilla extract.
Combine Wet and Dry Ingredients by gradually adding the dry mixture to the creamed butter mixture until a dough forms.
Shape the Cookies by portioning out 12 pieces of chocolate cookie dough, flattening slightly, placing a peanut butter ball in the center, and shaping the dough around it.
Chill Before Baking by placing the cookie balls on a lined baking pan and chilling in the refrigerator for about 30 minutes before baking at 350°F.