In a microwave safe bowl, add chocolate chips and butter. Microwave at 20 second intervals stir after each time until smooth and well blended. Allow to cool to room temperature.

Using a mixer, blend sour cream, vanilla, and salt into the cooled chocolate mixture. Then blend in powdered sugar a cup at a time until nice and blended.

Makes enough to give a nice covering to the top of a 9 x 13 cake.