Does anyone have any tips on where I can look for details on how to go about
designing/specifying/building a passively-cooled larder for a kitchen? We
are having some structural work done, and being able to incorporate
something like this would be great.
I've done a little search, but not really come up with anywhere good to
start.

Not a lot of use, I know, but I saw something on TV a while ago where
they went through the "mechanics" of a passive larder / cooler - I think
it had an opening to the outside, and IIRC there was a specific
combination of rock types for the interior surfaces.