Dark Chocolate Frosting

For quite a while I've been wanting to find a chocolate frosting recipe my family really likes.  I've tried some here and there, including one that uses cream cheese and sour cream.  I really wanted to love that one because it looks so beautiful piped onto cupcakes, but it just wasn't quite the taste I was going for.  One night I decided to make half batches of 4-5 chocolate frosting recipes and start taste testing.  My husband was a very good sport to help out with this project.  There were some good ones, but I kept my eyes open for more recipes to try.  Eventually I found this one and it's our favorite so far.  Some of the other recipes I've tried have a strong butter flavor, but this one does not.

I was using Hershey's Special Dark Cocoa for many of the frosting recipes.  It's a blend of natural and dutch-process cocoa.  I thought the frostings made with it had more of a grayish look rather than a rich, brown chocolate color.  Eventually I switched and started using unsweetened cocoa.  I much prefer the look of the natural unsweetened cocoa in frosting, and it tastes great too.

Dark Chocolate Frosting
Update 3/15: The last time I made this it was too thick to beat up nicely and I had to add in some extra cream.  I've updated the recipe accordingly.
Note: I decreased the powdered sugar by 1/2 cup from the original recipe.  If the chocolate flavor is too dark and you want to sweeten it a bit, you can add back in the 1/2 cup of powdered sugar.
Ingredients:
2 1/4 cups powdered sugar
2/3 cup unsweetened cocoa powder
6 tablespoons unsalted butter, softened
6 tablespoons heavy cream, plus additional tablespoons as necessary
1 teaspoon vanilla

Directions:
1. Sift together the powdered sugar and cocoa powder to ensure there are no lumps.  Set aside.

2. Beat the butter until creamy, for about 2 minutes.  Gradually add the sugar/cocoa mixture alternately with the heavy cream.  Beat on low speed after each addition.  Beat in the vanilla and continue to beat on high speed for 2 minutes, adding additional cream as necessary to reach desired consistency.  Add a pinch of salt if desired.

Source: slightly adapted from sallysbakingaddiction.com