In case you are wondering what double knitting is, I'll try to explain. Double knitting involves working with two strands of yarn (usually of different colors) in a manner that creates a two-sided, reversible fabric. One strand is knitted, creating the front, and the other strand is purled, creating the back. If you swap the two strands, you'll get a stitch of the opposite color. By doing this in pattern, you end up with a reversible fabric, with the same pattern in opposite colors. There are many helpful videos available.
As I usually do when learning a new technique, I started with a small project: a cell phone case. If this works well, I'll probably try something a little larger for my next double knitting attempt, maybe mittens or a hat. Now that I live someplace with real winters, those would be very handy!