I never, ever remove the chalaza and have never encountered anything untoward in my brownies, even when mixed by hand.

Like Carolb, I always mix my brownies by hand (much easier, quicker and less to clean up) and never bother to remove the chalazas. Without exaggeration I would say I have made hundreds of batches of brownies over the years (I used to make them as a fundraiser, 12 dozen every weekend for a few months and even now I make them for work and family) and have never had a texture issue.

I really don't know, but I don't think the chalazae would make a different texture unless they were at least partially cooked before they started baking. They should be incorporated into the batter. Unless, if you didn't fully beat the batter and left pockets of unincorporated egg, which could just be the regular white even. I don't think it would do that, since the sugar and fat liquify and should combine with even unbeaten or membranous bits of egg, but perhaps that could work. Were there nut in the brownies? Like maybe a bit of nut skin off of otherwise skinless nuts Mystery! I love a good mystery, and this seems a lot more intriguing that the murder and mayhem of fiction...

I mix my brownies with a spoon.....and do occasionally get a hard bit or 2, but I mark it down to unmixed flour or cocoa.

I am pretty "chalezea phobic" back when raw eggs were safe, I used to often drink an egg nog....and there better not be any bits in that! And I now make ice cream from pasteurized eggs....and again I remove the chaleaza....but never noticed it in scrambled eggs, nor a quiche. Don't know....does cooking make that icky bit harder or softer?

I wonder if a bit of the membrane may have gotten in by accident?

My only brownie recipe I have and make, is all done by hand. Quick and easy. Nuts, cocoa powder, butter, etc. I've never encountered anything remotely hard or tough or chewier than the rest.

I assume that's that spermy thing that you sometimes find on a too-soft-cooked egg?

plllog, you may have hit upon something. It is possible that I added the eggs before the butter/chocolate mixture was cool enough. Perhaps I got a bit of ”scrambled egg,” although I didn’t notice the eggs scrambling at the time. I know it is not nut related. I don’t add nuts.

jasdip, the chalaza (singular) or chalazae (plural) are the white stringy bits that hold the yolk of the egg in suspension from end to end in the shell.

It also might have well been a bit of something that did not get fully incorporated, but the more I think about it, the more I think it was a bit of cooked egg. Until yesterday, I had never attempted to remove the chalaza from an egg and I don’t recall ever noticing it as a separate part of a dish.

Oh, yes. If you did it fudge style and didn't temper the eggs, I think the most likely thing is cooked egg, as you said. That's a known thing, not just an inference of you associated it with egg so maybe it was unincorporated egg that magically didn't soak into the batter. I like to make the custard for ice cream very thick, so sometimes get those little strings of cooked egg, but it all goes through a fine mesh strainer, so I don't worry about it. I definitely think you figured it out.

I’m a fudgy brownie person 100%. DBIL scoffed at my brownies saying they were not done. They were done to perfection and fudgy as all get out!!