Handlebar mitts/pogies. Worth a couple of glove ratings all on their own. Definitely allow lighter/more flexible gloves without penalty. I use the MEC ones, but they need to be modified with brake cable inner fed through the opening seam, and cinched up to provide some stiffness to the openings.

Huge, huge difference. there are even some out there for drop bars.

As an added bonus, they provide some extra protection to the cable entries at the bar controls.