Super bulky cashmere yarn recycled from a sweater- I combined multiple strands together using a ball winder. The thicker yarn makes this hat warm, but also has the benefit of hiding the small knots- cashmere likes to break easily as it is unraveled- especially when you accidentally cut it! Winding multiple strands together makes it so that if a knot comes undone the whole hat doesn’t unravel.
The dark blue is leftover wool/acrylic from another hat- I love how fluffy it made the pompom!
PS- I long ago gave up making pom poms with cardboard/wrapping them about me fingers- which is always a disaster and involves lots of trimming. I use a pom pom maker with latches- mine looks like these which you can find on eBay for about $5. They work well enough if you only need to occasionally make pom poms, but are not as sturdy as the Clover ones (the latches on mine tend to fall off).