Can anyone tell me if after the pastillage has dried, if it can be cut easily if it were attached to the side of a cake? I'm debating trying it for a castle cake I have coming up, but I'm curious to how one would use it in that capacity having never used it myself.

Is it better used where it would just be popped off and then the cake cut? If its attached to the cake with buttercream, would it become mushy again after drying?

No, you really can't cut pastillage once dried. You would need to remove the pieces in order to cut the cake.

HTH
Rae

Pastillage gets very hard. You'd need to remove it before serving the cake, as there is no cutting through it.

I am new to using pastillage (I used it to make a wedding cake topper recently, check it out in my photos). It does dry very hard and would only shatter if you tried to cut.
If you still want to get a good solid shape without it being too hard. I would suggest you mixing the pastillage with fondant 50/50 mix. You may need to apply it to cake (if it is for sides to be sticking out) with royal icing not buttercream, as the buttercream may not be strong enough to hold it in place.

I hope this helps.

Hmm. First.. thank you. Second.. Has anyone ever covered the outside of a castle cake with pastillage? If so, was it a huge HUGE pain ( and or mess) to pop off the pieces before cutting? Perhaps I should just stick with using this stuff for the turrets? I'm guessing it dries quicker than gumpaste too?