Chocolate Frosting

I know, right?  A post on chocolate frosting?  I just need to memorialize this one because it's that good.  The consistency is the same a day later as when you frosted the cake.  Silk.

1 cup butter, softened
1 cup cocoa
1 t. vanilla extract
1/2 cup milk
4 cups confectioners sugar

In a large mixing bowl cream butter.  Sift the confectioners sugar and cocoa (I believe in this step) and add it to the butter mixture.  Add vanilla.  Add milk until frosting reaches spreading consistency.