if i make my cake the night before and add the pirouettes the next day onto the icing, will they stick or have a hard time sticking to the icing?
should i add them to the cake before i deliver, is 4 hours in advance to long?

If you use a crusting icing, they won't stick very well if you wait to put them on.

I have made 2 cakes using the pirouette cookies - both I made the evening before they were served and they were fine. If anything, they were the VERY slightest bit soft but it NO way soggy. They still had a strong crunch to them and didn't taste stale or mushy.

bump

I haven't worked with the pirouettes, but I think they would be fine to use a little bit of icing to secure it to the cake before you deliver it.

Since they are fragile, I wouldn't use too much icing and it would probably be better if the cake you were putting them on was room temperature and the frosting was crusted. Less likely to transfer moisture into the cookies.

I agree with awolf. I have made the pirouette cake, and even two days later the cookies still had a nice crunch to them.

probably why you see a lot of these cakes with a ribbon around them ... to help hold them in place. I have cake magz full of them set up with ribbons.