Preheat oven to 350 degrees Fahrenheit.
In a large mixing bowl, beat together butter, sugar, and brown sugar for 3-4 minutes until light and fluffy. Add eggs one at a time, mixing well after each addition. Stir in vanilla.
Mix in flour, cake flour, cocoa, and salt until well combined.
Gently fold in chocolate chips.
Pour the batter into a 9 x 13 pan and spread it evenly.
Bake for 28-36 minutes.