Pogies, but I don’t like em for harder riding, they’re on the fatbike but they’re too distracting and weird feeling for me to ever have been happy with them on the normal bikes (and even on the fatbike it can be problematic on steeper/rougher stuff). So they’re not a magic bullet.
For me bike gloves basically don’t cut it, I have cold hands. So I always say the same thing, Glacier Gloves Perfect Curves. These are bad riding gloves but they’re warm, and warm fingers in bad riding gloves is better than frozen fingers in good riding gloves. They’re made for window cleaners, they’re waterproof neoprene so completely unbreathable, you can’t wear them if it’s not bloody cold because they fill with sweat. They’re made of foam rubber basically so your contact with the bike isn’t so good, you lose feel and you get a lot of squish and movement, and if you get them muddy that gets even worse (though on the plus side, you can wash the mud off in snowmelt streams and not feel it). And they end up smelling like something’s died in them, because they’re hard to clean out and dry properly.
But they keep me warm, and no bike glove has ever kept me warm, and all those downsides are basically irrelevant when you’re doing a stupid kinlochleven winter race in the snow on scary terrain and you can still feel your fingers and brake properly, and not just be surviving but actually comfy. Or finishing a ride that you’d have bailed, or not having to finish a ride in actual pain feeling terrible. Or being able to throw a snowball at your mates ;)
They’re an extreme option but I love em. I’ll be very happy when I put them away in spring.