I think that quote is from near the end of The Silver Chair when a faun is describing what centaurs have for breakfast. But I'm sure pavenders are mentioned earlier in the book when Eustace and Jill stay at Cair Paravel.
The list of breakfast food for centaurs (at least the human part of them!) does sound rather Victorian or Edwardian and probably reflects Lewis's childhood. I don't think so many people now are accustomed to such a heavy meal so early in the day.
