Droste is one of my favourite chocolates, it's a Dutch brand but it doesn't get mentioned a ot here.
At Christmas I always buy Droste chocolate letters for my close family, usually the first letter of their name. It's quite a tradition in the Netherlands. There is a brief explanation at the Droste site here:
http://www.droste.nl/data/content/engels/assortment/season/s interklaas.php
You can also see all the different Droste products at the menu there.