From memory (uh-oh), take a big pile of cashew nuts, plop them in a blender (can't remember if you add water... probably, a little) and blend blend blend, then slowly dribble more and more sunflower oil into the mixture as you keep blending. The more oil (to a point), the stiffer (and fatter :P) the 'cream', until you get something that's whipped-cream-stiff.

I've tried this and it works great, it's just a matter of whether I remembered it right. ;)