I am making mushrooms for the top of a cake. I am wondering if I make them out of the meringue will they hold up when I place them on the buttercream frosting? What if I made them out of Royal frosting? Any thoughts? I am afraid they will "melt" if I make them out of pure egg whites???

I've made meringue mushrooms before with Bouche de Noel cakes. No problem with them melting when they came in contact with the chocolate buttercream. I don't remember them sitting in the buttercream for days . . . I think they were eaten up pretty quickly . . . so I'm not sure how they would fare if they were placed in buttercream and left there for a considerable amount of time. In any event, I don't envision them melting--maybe just softening a bit and losing their snappy crunch at worst.