Interesting spinning technique

I recently bought some handspun two plied yarn from Joybilee Farms (www.joybileefarms.com) for my Lumpy Knit Hats. It was spun in a way I have never seen before that creates a very interesting effect. There are two yarns plied together in the usual way except that one of them is randomly knotted. The knots look a bit like the crochet stitch known as the popcorn. So it appears that a medium fine spun dark brown yarn was plied with some hand painted red/orange, lavender, gray yarn of about the same weight. The hand painted yarn has the random knots. This is a technique I'd like to learn! I've made some pretty wild hats out of it, which you can see pictured here. They are also on my website.

The hat above is a long round cap that covers the ears or can be worn turned up. The one below is a Lumpy Knit Hat.