Galette de rois, or king's cake, is associated with Epiphany, which falls on January 6 and is linked to the visit of the Magi, or wise men, who were led to Bethlehem by a star.
In remembrance of this, some say, a figurine of baby Jesus was placed inside the galette de rois. When the cake was eaten, someone would find the figurine in their slice and would be called 'king' or 'queen' for the day.
Others say the tradition of placing items, which can range from gems or figurines to fava beans, inside the cake comes from a fable by Charles Perrault, a 17th century French writer, who also wrote the story of Cinderella.
One day, out of the blue, the king demands a cake, which sends the kitchen into a frenzy. While mixing the cake in great haste, the young kitchen maid, the unfortunately named Peau d'Ane (donkey hide), accidentally drops her ring into the mixture. As the king eats the cake, he finds the ring, and decides the ring's owner is the love of his life. He asks all the noblewomen to try on the ring. Of course, none of their fingers fits snugly, so he tries the ring on his staff. Finally, at the back of the kitchen, the grubby Peau d'Ane appears, and is a perfect match. Without blinking an eye, and to the horror of all those around him, the king declares her his wife. She's whisked away to be cleaned and clothed properly, and to everyone's surprise, she's an absolute beauty, and in a classic fairy-tale ending, everyone lives happily ever after.
There are several versions of the cake. New Orleans is known for a king's cake that is similar to a coffee cake. Within France, there are also variations. Provence is known for a brioche-like cake with candied fruits, while in Paris and further north, a flaky version filled with frangipani is common. The latter is said to have been introduced by the lover of Henry IV's second wife, Marie de Medici, a count named Frangipani, but that's a story for another day.