I use the Shrek principle viz
aka layers, lots of thin layers to trap and retain heat. That day I had on Burton thermal bottoms and a top, a wool thermal top and a deep-sea diver drysuit under top made by Weasel (as used by diver mates in the North Sea). I also had on an RS Taichi windproof onesie which is totally awesome. Thick wool-based thermal socks too. Oh, and heated grips FTW which allows me to wear gloves which let me actually feel the controls. If it gets colder I have a thin balaclava, a windproof neck sock and thermal glove liners. For the next level cold, I’ll add my wets (pants and jacket) and migrate to wet weather gloves and my emergency windproof under jacket.
Key is to keep the wind from going through you as that totally steals the heat from your body and once you’ve lost that heat it’s extremely difficult to get it back. Textiles are good here but I want the highest level protection possible which means that there’s no choice other than leather.
The windproof onesie
and emergency windproof under jacket