This mitten is too small.
That cute little mitten is the beginning of Hermione's Cable and Bobble Mittens from "Charmed Knits" by Alison Hansel, based on Hermione's mittens in "The Prisoner of Azkaban." The only sizing options, unfortunately, are by changing the gauge. Of course, I don't want to end up with the same problem I had with my first mittens.
My understanding of gauge has come a long way since high school.