when i was in ny recently, i had a whitefish bagel sandwich from essa bagels and just about died. it was a thick cut of smoked whitefish and it was seriously the next best thing to fresh sashimi.
i went to the bagel shop on national/sepulveda on chowhound recommendations but was sorely disappointed with their whitefish salad bagel sandwich.
know where i can get a sandwich like i did at essa in new york? it doesn't even need to be a sandwich, i guess....just smoked whitefish (or really good whitefish salad) is fine.
Hands down, the best whitefish salad I have ever had was at Brent's Deli in Northridge. It's wonderfully good. I've been to most of the big-name smoked fish purveyors in LA and Manhattan and I will confidently say that Brent's whitefish salad sits alone on top. They serve it with some good pickles, tomatoes, etc. and a few pieces of rye bread. It might even be in my list of top 20 things I've eaten in LA.
Second this. I live quite far from the area, but made the trek out to Brent's based on recs from this board when I was in the Valley. Got a quart of the whitefish salad and a loaf of their rye bread. They were very nice about giving me ice packs since I had a long drive home. The toasty rye bread with a huge dollop of the whitefish salad was one of the tastiest preparations of smoked fish I've ever had.
I used to get whitefish salad sandwiches in the Century City Mall food court but this was years ago when I worked up there. Not sure of the name or if it's even still there.
For a more "chunky" type sandwich I highly recommend Katella Deli in Los Alamitos. They have a whitefish sandwich called the "Grandmother Shirley". Very tasty. You can also get a whitefish platter and make your own sandwiches at the table, or even buy a whole whitefish to go. Delish.
Barney's Greengrass (top floor of Barney's department store in Beverly Hills). Supposedly, they fly in bagels & fish (lox, whitefish salad, etc.) from NY.
I've also bought whitefish salad at Whole Foods and it was decent. IMO, Bagel Brokers is the closest you'll find to NY bagels, but not sure if they have whitefish salad.