Laos style cuisine in the Northend?
A Thai/Laotian friend of mine took me to Viengthong a few months ago and I loved it. I don't know much about Laotian food, but my friend goes regularly and says it's pretty authentic. We had the Nam Kao, Squid Salad and Papaya Salad. They didn't dumb down the heat for us so watch out for that.
2820 Martin Luther King Jr Way S
Not in the northend, nor secret, but there is interesting Lao cuisine available at Vieng Thong and Thai Palms, in south Seattle. See http://chowhound.chow.com/topics/593526 . I enjoyed Thai Palms on my last visit, but I've heard the menu may have been slimmed down since.
What's the place you knew of? Kafe de Laos? http://www.kafedelaos.com/contact.htm
I've heard they keep very odd, limited hours. Have you tried?