Summary

This has become one of my favourite designs, as it can be used for birthdays Valentine's day, as a voucher, ... So it is really universal.
The idea is to pack a chocolate bar in the box and display the letters "du" in German or the letter "u" in English through a heart-shaped window.
I used duplo as a chcolate bar here, as it works as well in German as in English. And in between it is available worldwide, also not yet common and therefore a little bit difficult to get in the US. But of course you could do the same with any other chocolate bar that has a "u" in the name and where the letters are well known.