I didn't want to write a message on a Shinkansen (bullet train) shaped birthday cake for my son. I used mini cream puffs, which were originally for a decoration around the cake. I put leftover whipped heavy cream on top, and wrote the message on the cream so that it's easy to see the letters. They looked nice.

・You can use any kind of mini cream puff.
・Please add an appropriate amount of sugar to the heavy cream. If you use readymade whipped cream, it's really easy.
I used leftover whipped heavy cream from making the cake this time. Recipe by Ichigopapiko