I've been slowly finding a use for all things from Germany (going back next week if you want me to keep an eye out for anything so you know if you should go...) and just used my Pillsbury Croissants. It really is fun to pop open those cans...reminds me of making cinnamon rolls on the weekend (Will show you how to make those from scratch soon as well - my Grandma's recipe)
This was very simple to do. I wanted them cold but by the time I had the time to make them I was too hungry to wait. I think they'd be better though. You don't need a lot. Even if you haven't made it to Konstanz, you can still find the croissant ready made dough here - I found mine at Migros, but imagine Coop would have it as well.
What you need:
Mozzarella cheese (not pictured, sorry)
Chop up your tomato and cheese (if not using shredded)
Put a small amount across the fat end of the dough and then roll it up starting from the long end. Place the small end of the dough on the bottom while baking. Curve the ends in to make a crescent shape (I still need to work on this part a bit - or put less toppings inside).
Either refrigerate for a nice cool snack later or eat warm (just be careful of the hot tomato!).
I have also made these with just brie inside - they were very good! (eaten warm)