Couldn’t help casting these on!
I’ve made 2 tiny changes from the pattern. I used a long-tail cast on using waste yarn and main yarn tied together, as I didn’t have a crochet hook to hand when I was ready to start this project. The waste yarn then has to be picked out of the cast on edge, which is less convenient than the crochet chain (which unzips). But it was no trouble at all, and very easy to do.
I’m also not changing how I hold the yarn as I swap from palm to back of hand. I’m keeping the Islay (CC) as the dominant yarn throughout. I started trying to swap at the mid-point, but kept forgetting and was making a hash of it, so I decided it was better for me to be consistent throughout. If you look at the palm of my mitten though, you’ll see that the Haar zigzags are much less prominent than on Kate’s sample.