Buttonholed Cable Chain is of course a variety of Cable chain stitch and you need to be able to work a foundation of Cable Chain. If you need a refresher my tutorial for Cable Chain stitch is here
Cable chain differs slightly from regular chain stitch as Cable chain has an extra bar worked between each chain stitch. When you buttonhole this stitch it becomes something quite different.
When you first learn this stitch use a thread with a firm twist. When mastered experiment with other threads. The example is worked in Perle #5 thread. I worked each journey in different colours so readers could see what was happening.
Work a row of Cable Chain stitch which act as a foundation.
For the second part of the stitch work from left to right and bring the needle up through the fabric on the bottom the left hand side.
Slip your needle under the thread of the first chain stitch as illustrated. Loop the thread under the needle point and pull the needle through to make the first buttonhole stitch
Work a buttonhole stitch on the side of the chain stitch being careful not pass the needle through the foundation fabric. Add more buttonhole stitches along the bar until they sit snug.
As you work slide the stitches long the bar so that the finished stitches are spaced closely together.
When you reach the end of the foundation stitch move to the next chain skipping the bar between. The bar acts to divide each loop neatly but does not need to be buttonholed.
When you reach the end of the row turn your work and buttonhole the other side of the cable chain foundation.
How to work Alternating Buttonholed Cable Chain Stitch
Alternating Buttonholed Cable chain stitch is a variety of Buttonholed Cable Chain you start with a foundation row of Cable Chain stitch.
On the second journey work buttonhole stitches on the side of the chain stitch being careful not pass the needle through the foundation fabric. As you add more buttonhole stitches slide the stitches long the bar so that the finished stitches are spaced closely together.
When you reach the end of the foundation chain stitch slide your needle under the bar between the chain stitches and work buttonhole stitches on the other side of the next chain stitch. Work like this along line, buttonholing first one side of the chain stitch then on the next foundation stitch work the other side.
It is a fun stitch to work and I can see lots of applications for it.