I couldn't use mittens, heck I dislike insulated gloves. Hippo hands work great, but be aware, wind pressure will cause them to put pressure on the clutch and brake levers. Another thing is Baker hand wings or similar. Find some silk glove liners, warm, thin, and easy to wear. If you don't mind insulated gloves there are some ski gloves that have a pocket on the backside for hand warmers.