The Dunedain's
were imitations, but still effective, of that of the Elves, as the quote says.
Whether it was the same 'corn' i.e. grain derived from Valinor, but not tended by Eldar and so not infusded, generation after generation by their 'magic' or whether it was normal 'grain' tended with what 'magic' the Dunedain possesed we do not know. I tend to think that it was a special grain given to the Numenoreans, along with many other gifts, like the scion of the White Tree, and the Palantiri, and Aldarion and Erendis' birds.
The Elves and Valar were apparently free anmd generous with such things as were suitable to the Dunedain.
So we know from, the initial quote that the miruvor and waybread had some relationship to their elvish counterparts, so I imagine they were 'processed' in the same way, but were composed of simialr but 'lesser' [i.e. mortal]ingredients and magics.
But Aragorn having a stash of such semi-lembas might explain how he slept so little on the trip.
He may have been constrained by custom from sharing it with 'lesser' mortals except in the direst need. Or more likely, he had lived off the Dunedain versions [actually Arwen would have been in charge of it in Rivendell, when she was there, so he may have had the real deal for many years] and this may have altered his constitution to a such a degree that he could endure far, beyond normal mortal weariness.
[ April 17, 2003: Message edited by: lindil ]