(You can also hold together 1 strand of ww yarn and 1 strand of washable sock yarn for more warmth.)
2 stitch holders and yarn sewing needle.
Knitting needles sizes 5 and 7  (6 and 8)
Gauge with size 8 needles: 5 sts = 1"  6 rows=1"

Both mittens can be knitted at the same time.  Simply use 2 skeins of the same yarn, or yarn from the middle and outside of the same skein.  Cast on 2 mittens on the same needle and work across using the yarn from one skein for one mitten and yarn from the other skein for the 2nd mitten.  Works great!

CUFF- (using smaller needles): Cast on 28 sts. Work in ribbing of k1, p1 for 10 (12) (14) rows.

HAND: (using larger needles)
Row 1: inc 1 st in each of first 2 sts,  k across, inc 1 st in each of last 2 sts - 32 sts. 
Row 2: Purl
Row 3: Knit 
Row 4 and All even rows:  Purl
Row 5: K 15, place marker on needle, inc in each of the next 2 sts, place a marker on needle, k 15.
Row 6: Purl
Row 7: K 15, sl marker, inc in next st (increase by knitting into base of stitch), k2, inc in next st, sl marker, k 15.  Continue  to increase 1 st after first marker and before 2nd marker every k row until there are 12  (14) sts between markers.

(You are going to place some stitches on holders here, so you can work on the thumb)
Next row: (This is a purl row)
P16 (you will have to remove marker for the 16th stitch); slip those stitches to a stitch holder, p 10 (12) (this is the thumb); slip remaining 16 sts to another holder (removing the marker).

THUMB: Work even for 6 (6) (8) rows.  K 2 tog across next row.  Break yarn; leave end for sewing.  Run yarn through remaining sts, draw up tightly and fasten.  Sew thumb seam.

TOP: Join yarn at beg of 2nd holder, p to end of row purling right off the holders back onto needles.  Work even on 32 sts for 12 (14) (16) rows.  You can change colors on knit rows (right side of mitt)  if you wish to add stripes.

SHAPE/decrease TOP:
Row 1: (k 2 tog, k2) 8 times. 
Row 2: Purl  
Row 3: (k2 tog, k1) 8 times. 
Row 4: Purl. 
Row 5: K 2 tog across. Break yarn; run through remaining sts and fasten.
Make a 2nd mitten in the same manner. Sew up seams by whip stitching or use the MATTRESS STITCH so it's 'invisible'.

Fasten mittens together with a safety pin.