First I made a mould, out of a plate and two bowls. Unfortunately, the bowls weren't quite the right size, so I had to tie on the finished hat with a scarf, but never mind. Two layers of foil ensured easy de-moulding. I made two batches of brandy snaps, about four at a time, adding them to the mould at the stage when they were just solid enough to hold together, but still soft. In between adding snaps, I gave the hat 30 seconds or so in the bottom of the oven to melt them together. The whole thing has two layers of snaps, which provided reasonable structural stability. The whole thing was covered with clingfilm, inside and out, before wearing.
It was both pretty and tasty.
Edit: there's a bigger photo here. Sorry I don't have a better one.