The mittens are worked back and forth, from the bottom up, using a technique a bit similar to the Marisle technique, which alternates between garter ridges worked with one strand of each colour held together, and double knitting, where stitches are worked alternately in one colour or the other.
Increases are made along the way for the thumb, which is knitted back and forth in garter stitch.
The mitten is seamed along the outer edge, stitches are then picked up at the bottom edge, and the ribbed cuff is knitted in the round.