"Champamay Restaurant", near the roundabout in Champassack.
the menu is a bit frightening: soup and bailed dished, fired coyotes stuffed with pork/chicken...(get a good laugh before you order!), the food is excellent! we had a "big" dinner+beer for 80.000 kip (2pers).
the place is not easily overlooked: a huge open building on the riverfront.
the service is ok, you even get a mosquito-coil under your table (a necessity!)