These convertible gloves are the second in the Two Hands mitten series. The charts are the same size, so it would be easy to substitute the chart patterns into the other mitten. The first in the series is Two Hands Make A Heart

These mittens are knit from the cuff to the top of the hand, and feature a tubular cast-on cuff. The snowflake can be knit in using the intarsia method, or you can sew it on afterwards using duplicate stitch.

Techniques:
Tubular cast on
Duplicate stitch/intarsia
Increases/decreases
Kitchner stitch/grafting

Resources:
Long Tail tubular cast-on video by Ysolda
Duplicate Stitch Tutorial by Purl Bee
Kitchner Stitch Tutorial from Knitty
Intarsia Tutorial by Purl Bee
Intarsia in the round video