I just started another new one for my DH.. they are the only things he ever asks me to knit because he works outside and YES they are warm! the technique KQ described above is EXACTLY what I do. So, you can pretty much use ANY hat pattern with which to do it, just use the provisional CO.
OH.. one more thing. as you are knitting the first hat, keep good track of how many rows you knit before the dc's start... that way you are SURE the second hat will match!