I recently happened to stay almost across the street from the South End Buttery. It's probably not a big surprise when I say that this place is awesome.
I have to add that I never went after 10 in the morning, so I cannot comment on anything but their breakfast options and small bakery items which were, with the possible exception of their rather stale croissants, exceptionally tasty. Their coffee is good too, as is the general vibe of the place, which is very warm and welcoming.
The best item on the menu is their Dexter German cupcake, a delicious chocolate cupcake with a honey/walnuts/??? topping. In fact this might have been the best cupcake I ever had.
Pictures (l to r): Pecan Sticky Buns, Buttery Country Biscuit, Oatmeal w/ berries, Dexter German Cupcakes
Bottom line: Highly recommended.
South End Buttery
314 Shawmut Avenue, Boston, MA 02118