When you want to increase one knit stitch to two, there are not many ways to do it that are symmetrical. If you know of any others, let me know!
This way is probably not ideal, but I've seen none others like it.
If you're familiar with the "knit-one-yarn-over-knit-one" increase, that's the first step in this new increase. K1-yo-k1 is what I'll call it from now on.
K1-yo-k1 is a symmetric increase, but you've added two stitches when you work it. The way to turn this into a single decrease is to decrease away (symmetrically) the yarnover on the return row, leaving just two knit stitches symmetrically arranged.
Here is the increase:
Row 1, right side: Work to stitch to be increased. K1-yo-k1 in next stitch. work to end of row.
Row 2, wrong side: Work to increased stitch. Purl 2 together, the knit stitch and the yarnover. Slip the next stitch to the right needle knitwise, and replace on the left needle. Next work a "purl-2-together through back loops" of the stitch just slipped, using that loop and also using the left needle to pick up the left leg of the yarnover (that was just worked together in the first p2tog).
This is brand new, so I don't think the instructions are that great. A video would probably help.
I just wanted to stake my claim on this technique!