After finishing the boil and chilling the wort for my all grain batches I find I always have a large volume of gunk left of the bottom of the pot. I'm sure it's just spent hops and other solid bits from the mash, but it's so thick yucky looking I have not been adding it to the fermenter. The problem is it's a significant part of the batch, ends up being around 4l of a 19l batch.
My question is should I just dump it all in the fermenter and let it settle there, or is leaving it behind the right thing to do?