The Simplified Cast On is found on page 67 of RD KH.
The Simplified Cast On uses two strands of yarn and one needle. The little twists on the very edge run the opposite way the basic long tail cast on – going the same way as the stitches go if you knit them through the back loop, making this a good cast on if you are going to be using twisted stitches. It is reasonably stretchy – the stretchiest of the two strand cast ons that I’ve tried so far. However, the stitches on the first row (the ones that are made while you are doing the cast on) are a little bit warped. I don’t know if that is a cast on thing or a me thing.