I pretty much use a liner with a nice pair of Winter Pearls for most/all weather albeit bought a pair of Chinese "Bar Mitts" a couple of years ago for flat bar. Yes, they are bulky but you most definitely do not need a pair of winter gloves while your hands are on the bars. I was on my Fat Bike here on the trails in Chicago the other day when it was -2F. I rode for over 2 hours and my hands came nothing close to cold. They were quite toasty actually and I had on a thin Pearl Izumi glove liner with a Performance thin Neoprene glove. I could easily move my hands about within the confines of the Mitt and had no restrictions at all. I agree with the above post if those Mitts are on Drops. Your hands get so warm that you can easily take them out for a bit to change your hand position. These things are keepers. My commuter is fixed with flipped and chopped bars so I am asking the "Boss"*(**) to possibly make me a Neoprene set for them r/t the odd angles.
*wife
**she's also sews and such