It's made with two strands of yarn- one wool, the other this novelty stuff that I bought years ago, realized I had no idea what to do with it, and have been eyeing with desire and mystification ever since. It's perhaps slightly larger than necessary, but it's really pleasant to wear, so far. This is it with a bulkier scarf underneath.
The "pattern" as such is very easy. You start by crocheting a kippah/pancake of massive proportions. It should be just a little larger than you want the widest part of the hat to be.
Do one row without increases, then start decreasing (pull up a loop in your next stitch. then don't finish that stitch- pull up a loop through the next stitch, and finish the single crochet pulling through all the loops) with about the same frequency as you were adding before- maybe a little more frequently. Continue decreasing along your spiral until the opening is about the size of your head (I try it on every once in a while as it gets close).
Once it has, do several more rows at just that width. I did two rows with a nice alternation of front and back post half-double crochet around the bottom, so it feels snug and a little stretchy around my face.
And for kicks- here's how I used to wear berets. I still like it, it just doesn't work so well for me right now. But the hat is large enough to do this even with my hair underneath, which most berets can't manage...