Yesterday, I blogged about the hats that I gave out for Christmas gifts this year. I also gave out these fun mittens to match those hats (although I made far fewer of them). The pattern does not change for each size. Instead, you have to change the size of the needles, which does make the adult sizes a little less warm. You could of course just take the child size pattern and multiply it to make the size that you want for a warmer mitten.
You can knit them flat and knit them both at once on the same needles. All you have to do is knit one pulling from the center of the yarn skein and knit the other pulling from the outside of the skin. This is especially helpful when you are doing stripes, because you do not have to count as precisely (check out the photo below to see an example).
I had so much fun knitting these up. I used this pattern from the yarn lover's room.
Enjoy! Have fun.