The method here is exactly the same as preparing them for pesto, or really anything else.  The big green cones fall apart as they ripen.  It’s fairly easy to peel off the corm to release the nuts inside, that look like this:
ou can roast them at this stage, but I think they are better boiled or pressure cooked.  Boiling takes an hour or so, but pressure cooking is much faster.  I pressure cooked these for 20 minutes then cooled them, then cut them in halves and scooped out the nut.

There is a knack to doing this without cutting your fingers off.  Use a big heavy knife – the kind you’d use for a pumpkin.  Hold the nut with one hand, sitting it on its fat end, and get the blade of the knife dug in across the pointy end.  Shift your holding hand to the top of the knife and cut down.  Once you have the knack, it’s easy and fast.