This may well be no help at all, but here's a page headed "Las conservas: espárragos al natural" where you add salmuera, put them in "frascos" (which are surely jars), and then boil them for two hours. I have to say I would call this "preserving".
http://ileyconservas.tripod.com/id83.htmlAnd here's another, very similar, again with brine and again cooked in closed containers (tarros this time). The latter is the "conserva" bit, it seems. You have to check the vacuum seal afterwards. See pp. 15-16:
http://sallavor.org/resources/conservacion-alimentos.pdfThe method reminds me of my Manchegan mother-in-law doing rabbit en escabeche.