I think I finally have this worked out.
You can get two pairs out of a skein of Patons Classic Wool (210 yards/100 grams per skein) if you make the cuffs a little short. This is a great project for using up scrap yarn as long as it’s all the same gauge.
Yarn: Any Aran-weight (worsted weight, #4) yarn.
Needles: US2 and/or US3 double-points, four of each. This makes a snug mitt with a tight fabric. If you’d like a looser, stretchier, knit, use US3 and/or US4 needles. The smaller needle size is optional if you want it for the ribbing, but it’s not necessary.
Using either set of needles, cast on 28/32/36/40/44 stitches, using a long-tail cast on or any cast on with a similar degree of elasticity.
Divide among three needles: 10-10-8/10-10-12/12-12-12/14-12-14/14-14-16
Knit in 2/2 rib for 15/15/20/20/25 rows, or however long you want the cuff to be. The cuff will come up to the heel of the hand. Extra-small sizes might want to use a 1/1 rib for better snugness.
If you knit the ribbing on the smaller needles, switch to the larger needles for the body of the mitt (if you knit the ribbing on your larger needles, just keep going).
Knit all (stockinette) for 4/5/5/6/6 rounds.
Begin increase rounds:
Needle 1: Knit to last two stitches, knit 1 front and back, place marker, knit 1
Needle 2: Knit to last stitch, place marker, knit 1 front and back
Needle 3: Knit all
Round 2: Knit all
All subsequent increases:
Needle 1: Knit to last stitch before marker, knit 1 front and back, slip marker, knit 1
Needle 2: Knit to marker, slip marker, knit 1 front and back, knit to end of needle
Needle 3: Knit all
Round 2: Knit all
Repeat these two rounds 5/6/6/7/7 times, totaling 38/44/48/54/58 stitches on the three needles. You should still have 8/12/12/14/16 stitches on Needle 3.
On the next round after the last Round 2, knit to the marker, remove the marker, and place the next 10/10/12/12/14 stitches on waste yarn (that is, the yarn between the two stitch markers). These will become the thumb. Join the mitt back into a round after you remove the second marker by drawing the active yarn (the yarn leading to the skein) tightly across, bypassing the stitches you set aside for the thumb, to close the gap, and then continuing to knit the rest of the round.
There will now be 28/32/36/40/44 stitches on your needles, just like there were when you started. Redistribute them among the needles so that they are in the starting format, or at least about even, for ease of knitting.
Knit all for 8/9/10/11/12 rounds, or until the mitt is about an inch shorter than you want. This part doesn’t need to be precise; how long you make them is up to you. You will want to keep track of how many rounds you knit, though, so you can make the second mitt to match.
Change back to US2 needles and knit in 2/2 rib (or 1/1 if you were using that) for 8/9/10/11/12 rounds, or until the ribbing is as wide as you want. Bind off using Jeni’s Surprisingly Stretchy Bind-Off, which can be found in demonstrations on YouTube. If you can’t find it: Knit 1, wrap the yarn over the needle from back to front (moving the yarn towards you over the top of the needle; this is an inverted yarn-over); knit 1, then pass both the yarn-over and the first stitch over the second stitch. Inverted yarn-over, knit 1, pass yarn-over and previous stitch over, etc. I hope that made sense!
For the thumb:
Knit the stitches on the waste yarn back onto your US3 needles. Pick up a minimum of 6/6/4/6/6 stitches across the gap where you joined the hand back into a round, totaling 16/16/16/20/20 stitches for the thumb. If you need to pick up more stitches to prevent gaping, do so but then knit two together in the crotch between the hand and the thumb as many times as needed to achieve the stitch totals given above. You need a stitch total that is divisible by 4 so that the 2/2 ribbing will work, and you need to take up enough stitches so that the thumb isn’t too big.
Distribute stitches among three needles and knit all for 5 rounds, or as long as you wish (small sizes might want 4, larger sizes might want 6, etc. It depends on how much of your thumb you want covered. (Five rounds plus the ribbing below falls just below the middle joint of my thumb in a size medium mitt.) Change to smaller needles if you’re using them and knit in rib for 5/6/6/7/7 rounds, or until the thumb ribbing is as wide as you want. Bind off. Do not use the Surprisingly Stretchy bind-off as it is not needed here and will make the thumb opening too large.
Weave in the ends.