While I would never go so far as to devoting a whole blog to a single type of pastry, I have found some pretty cool ones out there devoted solely to brownies. Over the past couple of years, brownies have made their way to Germany as well, and they are now found as a regular item in bakeries and on cookie trays.
Sourdough is as old as humankind, or at least that is what I would like to think. This is how bread baking must have started: let a bowl with hydrated flour stand somewhere, and magically it rises at some point. It took mankind until the 17th century to figured out what organism actually worked that magic.