What sort of knitting trickery is this?

I’m tempted to say these ain’t your grandma’s brioche socks but who am I to know what kind of knitting expert she is. So, I’ll just say that these are very special knee-high socks with a stunning two-colour brioche pattern on the front that continues down the instep even though the sole is worked in one-colour stockinette stitch. And it does take a bit of knitting magic to achieve that. I’m going to recommend that you know your brioche before casting on for this pair. They are not difficult to make but do require concentration and slipping stitches back and forth.

Size
One size, to fit foot circumference 8-9.5’’ / 21-24 cm.

Even though the pattern includes only one size, brioche is a really stretchy fabric and should accommodate calf measurements up to 17.75’’ / 45 cm.

Yarn
Vuonue Wilhelmi (70 % wool, 30 % tencel 400 m/100 g) and Louhittaren Luola Väinämöinen (75% wool, 25 nylon, 400 m/100 g), or other fingering weight yarn. Shown in colors Light Grey (MC) and Antiikki (CC).

1 skein each.

The required yardage depends on the length of the foot, approx. 395 yrds / 360 m of MC and 220 yrds / 200 m of CC

Needles
US 1 (2.25 mm) circular needles (or dpns). Adjust needle size if necessary to obtain the right gauge.

Gauge
15 sts x 19 rnds = 2x2’’ / 5x5 cm in stockinette stitch (after blocking).

12 sts x 16 rnds = 2x2’’ / 5x5 cm in brioche (after blocking).

Other
2 stitch markers, a tapestry needle.