Alright hopeless romantic needing more advice.

[Metal Koola]

on the card with the chocolates write: Don't eat these all at once, you'll get really fat, and I won't like you anymore.

So seriously...

Chocolates are always good, and write something like "sweets for a girl who couldn't possibly get any sweeter" Something good like that...

The classic "do you like me, check yes or no" always works too.

another idea just came to me...

put a message underneath the chocolates, or possibly a photo of you two together.