She'd been afraid that the end of the conversation might prove a little more solemn, given that they were talking about stereotypes and the like. But Church seemed rather focused on talking about potato snacks, and the idea of discussing that rather than anything of any serious import strikes Hermione as bizarre... but not wholly unappreciated.
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"In case you haven't noticed, most of the people here are rather fit and trim; introducing the art of deep-frying to them would change that drastically. Besides, I would have assumed that you'd be more interested in introducing them to-... to fried chicken or cheeseburgers before you tried for crisps. Or are they just the easier thing to make?"