“What's that?” said Ron, pointing at a large dish of some sort of shellfish stew that stood beside a large steak-and-kidney pudding.
“Bouillabaisse,” said Hermione.
“Bless you,” said Ron.
“It's French,” said Hermione, “I had it on holiday summer before last. It's very nice.”
One of the dictionaries I've consulted says "Bless you" can be used to express "thanks", which I think it could be the author intended to mean for this context. But I don't have confidence. What does it truly mean?