The sleekness of the visuals here--the logo, menu, dining room design, even the name--may delay you awhile in discovering that this is two rather standard restaurants in one. It's half Vietnamese, and half American breakfast-and-lunch cafe. Both aspects of Thanh Thanh are a bit more than passably good. The pleasant surroundings and the hospitable staff explain the popularity of the place.
The name is pronounced something like "tangh-tangh." The menu translates it as "light blue on a clear day." It's owned and managed by the younger side of a Vietnamese family that came to New Orleans as refugees at the end of the Vietnam war, and quickly set about making something of its new home. Thanh Thanh opened shortly after the hurricane in Algiers, but within a year moved to this location in the heart of Old Gretna. The proximity to the courthouse gives it a robust regular breakfast and lunch clientele.
The restaurant occupies an old Greek restaurant in an older building, and doesn't look like much from the outside. The dining room, however, is beautiful and comfortable, and feels like the kind of place where the music you hear in a spa ought to be playing. The young service staff is very pleased you're there.
The basic breakfasts and lunch are really not bad, but that's mostly for people who have to be near the courthouse. The Vietnamese food is what you crossed the river to get. At dinner, try some of the dishes that have a Vietnamese-Creole ring--the ribeye steak, for example.