Epiphany in detail.
Why am I attempting this? Bruno, feel free to correct any of my errors in explaining this French tradition. I know other Christian countries also celebrate Epiphany, some more so than Christmas.
Epiphany (6th Jan) celebrates the arrival of the three kings with their gifts. If you have a sister who lives in a French-speaking country, she can buy a pretty cardboard crown and little ceramic king and send you the recipe for the galette des rois, which I would describe as an almond paste pie. Very yummy. You hide the king in before baking and whoever has the piece with him inside gets to wear the crown. I think it is called a feve because it used to be a hard dried bean.
Further details Bruno? Does the finder of the feve get to be king for a day? Do people ever put money or other things in the cake? And why can't you bake any old cake recipe? And what does galette mean?
The above pic is a google image, and I think the little man looks more like a pastry chef, or a pastry chef apprentice than a king. Which could perhaps put someone in the position of pastry chef apprentice for a day. Wearing a crown.