This year I only just learned about the brioche stitch, let alone that there was such a thing as double brioche. But this hat makes me want to know more. I love how sculptural it is and how it could be done in one colour or contrasting colours.
I have no idea what double brioche even means or entails but I am very tempted to try this pattern.
Olga includes a note on her pattern page:
Double brioche is a unique stretchy stitch pattern that has been largely unexplored due to its complexity. ORU hat combines both brioche and tuck techniques to ease up the execution process. In making of this hat you will also learn special decreases that help shaping of the crown without interrupting the pattern flow inside or outside, rendering it completely reversible. Solid or bicolor versions are presented with options for shallow or deep crowns. This allows for various ways of styling of this doubly warm hat!