That's odd, they substituted the (Double) Gloucester and Cheshire cheeses - are they not possible to obtain in the US?

Looks like a tasty recipe. We might try that (although a member of the Household is lactose-intolerant, so I'd better get the lactase capsules ready if we do).

I've always added eggs. Also a bit of Worcester sauce, which is worth trying almost anywhere you get cheese or need a savoury flavour (providing no-one's vegetarian/etc).