Cream butter for a few minutes with a mixer on medium speed. Turn off the mixer. Sift 3 cups powdered sugar and cocoa into the mixing bowl. Turn mixer on the lowest speed (so the dry ingredients do not blow everywhere) until the sugar and cocoa are absorbed by the butter. Increase mixer speed to medium and add ADAMS BEST VANILLA, salt, and cream and beat for 3 minutes. If your frosting needs a more stiff consistency, add a little more sugar. If your frosting needs to be thinned out, add additional cream, 1 tablespoon at a time.