That is definitely an American buttercream, a combination of butter, shortening and powdered sugar. I like seriouscakes recipe, www.seriouscakes.com. You don't need a crusting buttercream, but definitely an American buttercream. If it is going to be outdoors, you'd want at least 1/3 of your fat to be hi-ratio shortening, like Alpine or Sweetex. You could do that with Swiss Meringue Buttercream, but if it gets hot it will not be very stable.
4/9/13 at 5:31pm