Appears to be magic mushrooms, which tend to be on the gritty side. A person who bit into the pbj sandwich would instantly know from the taste there was something amiss.
I know. I'm a kill joy.
Indeed....it would be a "no-brainer" to puree those "shrooms" to a paste. or powder....but maybe the user's already lost a significant part...
Please let me know how that worked out. I'm contemplating something similar.