This one will haunt me for awhile! First off, I could not find light corn syrup - I used agave syrup instead. Secondly, I could not find gelatin sheets so I used powdered gelatin. I think the agave syrup is what made things not turn out so well....I could not reach the soft ball stage as it was going to boil over the pot. So the marshmallows did turn white and sticky but they never really sat. My "cutting them into squares" turned into me slowly pouring it into the pot instead.
That said, the recipe was not a complete ruin. It still tastes ok, but the agave syrup makes it unbearably sweet. Too much effort for this cake than what it is worth..
Note, the "icing" is supposed to be solid.