During many of my stays in chennai I visit MuruganIdli shop in T.Nagar. Being a north Indian I love they way tge present their dishes. You get to eat in the traditional south Indian style. A banana leaf serves as a plate. Order for idlis and they fetch you fresh steaming ones.
That is coupled with multiple varieties of chutnies, whose names I dont know yet but the tastes I relish. They also have a unique way in which they serve water, they put plastic disposable glassed within a steel glass holder.
I also love the sweet pongal, stay away from it if you are calorie conscious, as it has tons of Ghee.
Must visit place for light snacks.