My personnal pick when it comes to link a small object with a deck of cards is to perform "Sure Bet". While it is shown with coins in Ammar's Easy to master coin miracle 1, it work really well with various things such as rings, tumbtacks (don't ask!) or bills!
Can't really tell you how to perform it (if you don't know "Sure Bet") but the simple effect consist of having the spectator choose 2 cards, then the deck is put aside, you shuffle and show the two cards again and again then the chosen object "appears" in between those cards.
I'm pretty sure making chocolates appears in a deck of Cadbury cards would be great, good luck
