There is a fantastic little eatery near the corner of Schustenstrasse and Charlottenstrasse called Back to Coffee. It has a great selection of freshly baked croissants in all different flavours including ham and cheese plus loads of fresh made baguettes and pastries and cakes. You can sit in there for as long as you want  with a giant latte for under 2 euros. It's got a lovely atmosphere and very friendly staff and you're made to feel welcome and it's very popular with the locals.

Also if you fancy a walk first, there is a lovely delicatessen on Dorotheenen Strasse called Splendid. It's a proper fancy little deli with down to earth prices. It sells the most fancy little pastries and little flans. It is very relaxed and you are not made to feel rushed at all.

Both of these places are not in any books, though they both are highly recommended.