Thank you everybody for your answers. I've knitted the cowl as described in the pattern (the shorter one) and I'm very happy the way it turned out! I've knitted it in only one day.
Can anybody suggest me super chunky yarn? (for needles 15 or 17) I would like new yarn that is in the same price range and thickness as Seriously Chunky yarn, but that it has a bit of wool (Seriously Chunky yarn is 100% Acrylic)