It looks like a semi-rustic finish. I would think that it would be achieved by laying on a thick layer of buttercream, then using the tip of your spatula to lightly scrape off bits to create that design.
You could practice first just by slathering some buttercream on a flat surface and working with it until you get the look you like.
AI've never done this, but it looks like it might be spatula work. Looks like they iced the cake smooth, then went over it with a spatula to make the effect.
Thank you soooo much!!! I really appreciate the help. It makes sense what you both said. I am going to try it first. The wedding in not until Aug. I am new to this site and I am already loving it. Thank you again. :)
The whole advantage of this is that you don't have to ice it really smooth since you are roughing it up anyway. Just lay the icing on smooth-ish and work with a spatula or spoon to get the effect you want. Lots of variations-vertical, horizontal, rougher, smoother, random, etc.
AI would venture to say you cannot do this well with a crusting buttercream, a meringue icing would be best for it. If you use a crusting, try adding a lot more liquid, so it crusts more slowly, or use water on your spatula, or mist your cake with water.
Or just keep moving, you wouldn't want to be messing around with it forever so that you have to fight the crusting. This is one you just put it on, mess it up and be done with it.
Thank you very much. I love all the tips.