Esbit. Cold weather wreaks havoc with alchohol vapor pressure, limiting stoves to to open flame and updraft types.

I've used homemade "hobo" stoves which operate on the same principle as the Ranger/Volcano stove. Messy, but very hot. If you're going to go with a twig stove, give some thought to woodgas stoves. They're supposed to be a lot cleaner then hobo stoves.