Non-PRO English Art/Literary General / Conversation / Greetings / Letters

Hi everyone!
This is from J. Austen's Sanditon:

The situation is that three siblings, all of them -Arthur included- rather sickly, have just moved from a hotel to their lodgings...
"...Arthur had found the air so cold that he had merely walked from one house to the other as nimbly as he could, – and boasted much of sitting by the fire till he had cooked up a very good one.”

There is nothing in the context to suggest that Arthur cooked up something like a story. The young man is, though, lazy and fond of eating and drinking, and uses the familial tendency of hypochondria to mask his laziness.

I wonder if his cooking up a very good one has anything to do with his warming his bones by the fire, otherwise I have no idea what the sense could be and I haven't been able to find a clue, and I'd be grateful for any information.

Thank you