Eight little cream puffs

In honour of Couldn't-Care's birthday, Lulu has baked a beautiful tiered cake that is supposed to be the pièce-de-resistance of the birthday party thrown after class in Do-it-all's workshop. But, during the day, a mysterious thief has eaten all of the cake, leaving only one cream puff behind. Who could have done such a thing? Lulu is going to investigate the matter, inspired by Rififi the Mouse, the famous investigator of children's books!