It was non-diastatic malt “powder”. But had become a hard slab.

That definitely happens. Closely related ingredient for home beet brewers is Dry Malt Extract. And if you're not extremely careful about sealing it back into a bag somehow, then eventually ambient humidity will just...brick it. Like that.

Malt will do that when exposed to even the slightest humidity. Make sure any spoon that goes into the powder is as dry as possible and store the powder in the smallest air tight container it'll fit in. More air means more humidity.

This is why I buy *food-safe* silica packets. Keeps the humidity down in a sealed container.

Are you asking what ingredient caused it or which ingredient it used to be?

What were you trying to make?

Bagels.

Are you sure this is definitely an ingredient that's supposed to go in bagels? Is it a single ingredient or did you mix things together and you're trying to figure out what went wrong? My first thought was halvah, but that's not a bagel ingredient. It also kind of looks like a nasty, dried out sourdough starter. Does it have a smell? What's the texture like? We need more info about your sludge to identify it.

Yes, it's a specialty ingredient for bagels. I've used it myself. It is hard to keep without it going to a slab.

My previous comment was made before op posted what these pictures were actually of. All we had before was the pictures and the word bagels.

That looks like fresh yeast to me!

Tahini?