Mitt (make 2)
CO 44 sts (I do the one handed cast-on over two needles to make it nice and stretchy!), join in a round.
K2, P2 for 20 rows.
K another 16 rows(ish, for the length of the thumb to the wrist)
Next row, m1, k to end.
Next row, k even.
Next row, m1, k1, m1, k to end.
Next row, k even.
Rep last two rows, making 1 at the beginning and end of the newly made stitches (stitch marker might help with this) and then knitting even, until you have 11 new stitches.
Transfer these stitches to waste yarn, CO 2 sts, and then continue knitting.
K 3 rows, and do a double-decrease of your choice to lose the two extra stitches that you cast on. You should be back to 44 stitches.
K 4 more rows.
K2, P2 for 8 rows, then bind off in rib.
Topper
From the two CO stitches you made after holding the thumb stitches with waste yarn, count 20 sts across.
For right mitten, insert tapestry needle threaded with yarn before the first CO st and pull through to the inside.
For left mitten, insert tapestry needle threaded with yarn after the 20th st and pull through to the inside.
For both mittens, using the point of a dpn, insert from the front to the back in the centre of the rightmost st, catch the yarn around the needle, and pull to the front. (This will take a couple of tries, but makes the topper's join practically invisible when worn over the fingers).
After joining the 20 sts in this manner, CO 24 more sts (you might have to do this purlwise, backwards, but it will turn out the same.)
K2, p2 rib the "hanging" stitches, and k across the "attached" stitches, for 7 rows.
K 11 rows.
Rearrange stitches across four needles so that they all have the same number of sts, if not like this already. You should be starting at the rightmost side of the joined edge of the topper.
SSK, knit to last two stitches of needle 2, K2tog. SSK, knit to last two stitches of needle 4, K2tog.
Knit next row even.
Repeat last two rows until 24 sts remain, then decrease every row.
When 4 sts remain, cut yarn, thread through four live sts, and pull tight.
Pick up three sts near the top, complete a 16 row icord, and kitchener stitch it together on the other side.
Thumb
Put held thumb sts back on needles, and pick up three more (the two cast on sts, plus another.)
Knit around, decreasing twice. 12 sts remain.
Knit 16 rows or until thumb is as long as your own thumb.
K2tog around, 6 sts.
K2tog again, 3 sts.
Cut yarn and thread through three live sts, pull tight.
Sew buttons where your icord loop hits the wrist, and enjoy!