You should actually take both stitches, as knitted - like... start to make a k2tog, but instead of wrap some yarn on the needle when you insert it into the stitches, just take those two stitches on your right needle. The way they are when you inserted the right needle for the k2tog. Now put them back - not the way you took them, just regular, normal purl-wise. Now your second - before - stitch is first and the first is second. OK, this part is like a cable stitch. But they are also twisted. If you work them normally, you would get a twisted cable. So you knit them through the back loop. What you will came up with is a decrease with a opposite slope to the normal k2tog. This is maybe one of the... well, numerous ways to do it - and they are all very similar, but also slightly different in looks.