* Three cake France is a humorous mispronunciation of "three-card monte", a street gambling scam.
* Finding a bean is a play on the idea of "finding a card" in the scam.
The Joke: The joke lies in the absurdity of the idea of finding a bean in a cake, particularly in France, and the mispronunciation of the scam.
So, what do you get? Nothing! You'd just be tricked, like in the actual three-card monte game.