Brioche Stitch (brk / brp)

Intermediate Textured

A plush, squishy two-color-capable stitch built from yarn-overs knit together with the stitch below.

Cast on an odd number of stitches.
Setup row (WS): Knit 1, then *yarn over, slip 1 stitch purlwise with yarn in front, knit 1; repeat from * to the end.
Row 1 (RS): *Yarn over, slip 1 stitch purlwise with yarn in front, then knit together the next yarn-over-and-slipped-stitch pair from the previous row (this is the "brk," or brioche knit); repeat from * to the last stitch, knit 1.
Repeat Row 1 for every row after the setup row — brioche has no wrong side once established, since both sides look essentially the same.
To bind off, work a stitch at a time as if in pattern and pass over, treating each yarn-over/slipped-stitch pair as a single combined stitch.

Brioche fabric is roughly twice as thick as plain rib for the same needle size, thanks to the trapped yarn-over loops — expect to use noticeably more yarn.
Two-color brioche uses the exact same mechanics, just worked in two passes per row (one color knitting, the other slipping) rather than one.
It's easy to lose your place in brioche — a row counter and stitch markers at pattern repeats help more here than in almost any other stitch.