I’m guessing that’s exactly what they’re talking about, dreams you have after eating something like Welsh rarebit! It was commonly believed that heavy foods, like bread, and foods like cheese could give you vivid dreams - and nightmares. It’s still “a thing” today, and while I totally thought it was just an old wive’s tale, apparently there’s at least some truth to it: here’s an NPR (All Things Considered) article.

Here’s an excerpt: 

Mr. WHITE: Well, as far as we can tell. What we found was that those who were eating blue cheese, Blue Stilton, were coming up with some quite vivid dreams that I’m sure the sleep psychologists would have a field day with in terms of interpreting.

BLOCK: Can you share some with us, or are you bound by science cheese privileges?

Mr. WHITE: Yeah, I mean, one of the volunteers said that she dreamed of a vegetarian crocodile who was upset because he couldn’t eat children. And another one dreamed that they had soldiers fighting with each other with kittens instead of guns.