5
Refrigerate crumb-coated cake 1 hour. Pile remaining frosting on top of cake, and spread evenly over top and sides, making as smooth of a frosted surface as possible. Decorate cake with marshmallows by placing them in neat rows around outside of cake. To decorate top of cake, start with a single marshmallow in centre, and encircle it with rings of marshmallows until cake is completely covered in marshmallows.