Heat oven to 350. Spray 2- 9" round baking pans w/ cooking spray. In lg bowl, combine butter, sugar, eggs and vanilla. Beat on high w/ mixer for 3 mins.
In another bowl, combine flours, baking cocoa, baking soda, baking powder, and salt. Add alternately w/ water to butter mix. Beat just until combined. Pour evenly into pans. Bake 30-35 min, or until a toothpick inserted in center comes out clean. cool.
Remove cooled cakes from pans. Place chocolate chips in microwaveable bowl. Microwave on high for 1-1/2 mins, stir. Microwave and stir until smooth. Whisk in powdered sugar and milk until smooth. Frost cakes.