My cold weather skiing has been in plastic shell double boots designed for mountaineering and compatible with ski bindings. For really cold condition, I was carrying full nylon and neoprene over boots that would accept crampons but not ski bindings. On this trip (Denali), we spent a lot of time at a camp at about 14,000 feet. We wore the classic "mickey mouse" over boots which were unfailingly warm and comfortable, down to -80F windchill, the coldest I have ever been. Those, unfortunately, will not play well with either crampons or ski bindings.