Answer:
Modern day bakers fill King's cakes at Epiphany with any number of fillings -- cream cheese, apple, cherry or almond paste. The filling is not purposefully "hidden," however. What is often hidden in a King's cake is a bean or coin as a token of favor to the finder when the cake is eaten. This "chosen one" is sometimes crowned "King" or "Queen" in celebration of the Magis' visit to Christ.