Haven't tried it but I've been given the impression it has a lot in common with breton and normandy style french ciders - that is a good blend of specific apples, crushed, pressed and left to ferment naturally (no added yeast) till the preferred sweetness level is reached. Character is extremely reliant on apple variety, blend of the above and the indigenous/inherent microflora. Vintages may be blended.
I love the french ciders and have made an (amateurish) attempt to reculture from commercial varieties with very limited success. I did once make a delicious slightly funky cider by adding commercial bottle dregs but the techniques and ingredients of commercial cidre makers are difficult to replicate on a small scale.
There is a good outline of the french process somewhere on the net though - maybe that coupled with that weird Spanish pouring method might be a start? A quick search couldn't find the one I was after but google breton cider, keeving and le chapeau brun and some good info should come up.