They are real mittens with a proper little thumb as well!
Using DK yarn and 3.25mm needles
Cast on 20 sts and rib 4 rows (K1,P1)
Work 4 rows in stocking st
Thumb: K12 and cast on 2 sts, turn and P6. Work 2 rows stocking st on these 6 sts. Next row: K2tog 3 times. Next row:P2tog,P1. Next row: K2tog and pull yarn through to secure. Sew up thumb seam and turn right side out.
With right side facing pick up and knit 4 sts from across bottom of thumb, knit across remaining sts to end.
On all sts work 5 rows
Next row (RS facing): K2tog, K6, K2tog, S1K1psso (slip 1, knit 1, pass the slipped st over), K6, K2tog
Purl one row
next row: K2tog, K4, K2tog, S1K1psso, K4, K2tog
Purl one row, then cast off knitwise. Sew up side seam. Job done. Make a second and join with ribbon or, as I did, a crocheted chain.
If you decide on stripes make it a 2 row pattern and this falls well when doing the thumb.
For the heart: start the pattern on the first full purl row after the thumb has been worked. For the first mitt P5 then P1 in contrast colour, purl to end in main. On the knit row do 3 sts in contrast using the first as a centre guide. Next row 5 contrast, next row 2 contrast, 1 main (which is in line with the first centre purl in contrast), 2 contrast immediately above the previous row. Continue in main.
For the second mitt, ie the opposite hand start the pattern on the 16th stitch- purl 15 in main, 1 in contrast....etc. This way the pattern appears on the back of each mitt. I hope the instructions aren't too garbled!