If the toxicology results do indicate that DC mushrooms were ingested by the victims, will EP argue that it was accidental? Either admitting they were foraged or sticking to the Asian Grocer line?
In an imagined scenario, where the cook is unaware that they have inadvertently used a toxic variety of mushrooms (whether foraged or bought) I picture the cook preparing the mushroom duxelles, simmering them away with herbs and wine and such, and wonder: wouldn’t it be normal for the cook to taste test this mushroom mix?
If so, and the mushrooms are indeed toxic even in very small doses, wouldn’t the cook exhibit some symptoms of poisoning earlier than the guests?
As much as I would like to think this was an accident and EP has dug herself into a bit of a hole with the lie about the dehydrator, I am leaning toward two beef Wellington dishes being prepared for that lunch.