Cream the butter, sugar and brown sugar together. Start on a slow speed until blended, then turn it up to the highest speed until it is light and fluffy. Add the eggs and vanilla to the mixture and mix on medium speed until the eggs are fully broken up and combined. Do not over mix this part. Sift the flour, baking powder, and salt together, add to the mixture and mix until combined. Add the sour cream and buttermilk and mix until combined. Add the espresso, and mix until it is combined. If you are using hot espresso shots, then pour them slowly into the mixture so that it does not begin to cook the eggs. Add the chocolate chips and mix them until combined.
Preheat the oven to 275 degrees F. Grease and flour a bundt cake pan.
Scoop the cake mixture into the prepared pan. Place the cake on a cookie sheet and bake for 1 hour and 45 minutes to 2 hours, or until an inserted knife comes clean from the cake. Placing the cake on a cookie sheet is just a suggestion to keep your oven clean, in case the cake mixture spills over the sides of the pan.
Let the cake cool, then remove it from the pan upside down. Garnish it with powdered sugar.
Recipe courtesy of Cafe Ladro