Preheat oven to 350 degrees F.
In a large bowl beat butter, sugar and vanilla until well combined. Beat in eggs until well combined.
Add in flour, cocoa, baking soda, salt, espresso powder, dry pudding mix and mix to combine.
Add in buttermilk and stir until combined. Fold in chocolate chips.
Transfer batter to a bundt cake pan (at least ten cup capacity) that has been sprayed generously with non-stick cooking spray.
Bake at 350 degrees for 30 minutes, reduce temperature to 325 and bake for approximately 30-40 more minutes or until a cake tester inserted into the center comes out clean. Remove from oven, allow to cool for at least 15 minutes before removing from pan.