In reply to angry pirate:
Been searching for decent mitts for a while until I found The Heat Company.
I've been using their shell mitts in -10 to -20 in Norway with strong winds both out at sea and on the mountain and they have been amazing. These take a sort of opposite approach - you can wear regular gloves or liners and then throw the mitt on over the top. You can then unzip the palm and fold the top of the mitt back secured by magnets, exposing your gloved fingers (used with Arcteryx Alpha MXs).
They're incredibly warm, although they are HUGE. You can definitely wear them without glove/liner but I haven't noticed any issues with warmth when zipped up either way. I've even found unzipping the palm and poking my fingers out but leaving the loose flap covering the backs of fingers a great compromise as it protects from wind and cold extremely well but you keep all the dexterity of bare or thin-gloved fingers. Even found my hands getting too hot when idling and using the zip to dump heat.
Only downside is they're bloody expensive.