Sharing is caring when it comes to a lot of things, and food in Here Be Monsters! is definitely one of them. Through food imagery, we get an idea of which characters are emotionally available/nurturing, and which are as caring as a dead tree trunk.
When Arthur shows up at Willbury's place, lost, alone, and confused, Willbury feeds him hot cocoa with toasted buns. The next morning, after drinking some more hot cocoa, Willbury uses "the cocoa bucket to make porridge" (7.26). While hot cocoa may not be something you'd want to eat everyday, it's rich and comforting. Willbury also gets Arthur some savory meat pies to eat (which they then share with Marjorie). We can see through these foods that Willbury cares about Arthur and wants him to be comfortable and happy.
To see the opposite sentiments in action, check out what Snatcher's goons try to feed Arthur when they have him imprisoned: "The porridge Arthur had been given was so cold it was almost solid, but he was so hungry, he tried to eat it. He'd not been given a spoon so he used his fingers to scrape it out of the bowl. It was a very slow process" (41.1). Arthur's captors clearly don't care about him, and that's why they're feeding him that disgusting gruel, plain and simple.
We see more examples of foods being shared among friends that tend to be delicious, but thankfully we don't see too much more of that icky gruel. Cheese plays an important role in the book, too, so be sure to check out what we have to say about that elsewhere in this section if you're interested or just looking for some more food for thought.