This stitch is just a Palestrina stitch with an extra knot on each knot. This makes the knot look bigger and fuller.
You need to know the Palestrina stitch to be able to do this stitch.
|Fig 1: Lay one Palestrina knot on the stitch line as illustrated.
Now make another similar knot over this knot.
|Fig 2: Take the needle beneath the base stitch without plucking the fabric underneath or the threads of the first knot to make the second knot.|
|Fig 3: Continue this process of making such knots.||Fig 4: A finished line of triple Palestrina would look like this.|