I grew up mainstream Orthodox in the 1970's and 80's in Brooklyn. I went to a boys' yeshiva day school in Boro Park in the 1970's and early 80's. We had very frum rebbes and the student body ranged from Modern to Yeshivish.
I NEVER heard of Shlissel Challah in all that time. Not from my rabbeim, not from my friends, not from my yeshivish relatives.
In the 80's I went to a high school that had a fair number of modern kids, but the basic tilt was fairly yeshivish. During my entire time there, I NEVER heard of Shlissel Challah.
After high school I went to yeshiva in Israel for a year. Again, Shlissel Challah never mentioned, not once.
My entire twenties (admittedly when I got more modern and spent a lot of time on the Upper West Side)? Not a single mention of Shlissel Challah, by anyone.
I got married in my early 30's. We lived in several Orthodox communities since then, in NYC and in the midwest. Never heard of Shlissel Challah. No one made it, no one brought it up.
When did I first hear of this deep and ingrained minhag? Only 4 years ago. From a blog. When Eliyahu Fink wrote a guest post on Dov Bear's blog about it. He wrote:
"Unless you live under a (very litvish) rock you know that this week is Shlissel Challah Week."
My response: "huh?"
Even since then, I've never been at ANY Shabbat meal where this was actually practiced.
I suspect that until very recently this was only practiced by some chassidim and chassidish wannabes, and has just exploded in popularity in the last half dozen years because it sounds fun. Or, like upsherin, it sounds frum to some people because chassidim do it, so they started doing it too.
I'm willing to bet that a great many of you are just like me, grew up as Orthodox "insiders" but never heard of this minhag till relatively recently.
When did you first hear about it?
Any kosher bakers out there? When did your bakeries first start offering Shlissel Challah?
This is how very fringe minhagim become mainstream and almost obligatory.