In all the years I've been riding, I've never come across a better solution to keep my hands warm in the winter
Tucano Urbano hand grip covers with heated grips.
The covers are made from neoprene, are virtually 100% waterproof and draft free and with heated grips, you only need to wear the thinnest of gloves.
I use this combination on my Honda for commuting and my hands are toasty warm.