I used a modified version of this pattern: the Margot Mittens on Ravelry.
My first attempt was a bit too small and the thumb was way too skinny & long. So I looked at this pattern to help me adjust it ever so slightly to make the corrections: Grammy's Mittens on Ravelry.
The cord is just an i-cord and I picked up stitches from the first glove to start it and then cast on stitches for the second glove so that it was one continuous strand of yard. Hopefully it's strong enough not to break at the hands of my niece.
Now to try them on her and hope they actually fit this time!