Measure the circumference of your mug and its height. A standard 350 ml mug is roughly 28 cm around and 9 cm tall. Chain enough stitches to match the circumference minus 3 cm (the cosy will stretch). For a 28 cm mug, chain 44.

Work in rows of sc until the piece is as tall as the mug. For a 9 cm mug, you need approximately 10 rows at worsted tension. The rectangle should be firm and not floppy.

Hairline: join black yarn to the top edge. Work sl st across the first 6 stitches, then (ch 3, sl st into the 2nd and 3rd chain to create a point, sl st into the next stitch on the cosy) repeat 4 times, then sl st across the remaining stitches. This gives a jagged hairline silhouette.

Embroider the face: two white yarn loops or felt circles for eyes, then a black cross stitch over each white circle for the classic Frankenstein pupil. Four straight black stitches in a square on the lower right cheek area make the neck bolt detail.

Seam the short ends together at the back with a whip stitch, leaving a 3 cm gap about 4 cm from the base for the handle. Sew a button to the front if desired and leave a chain loop at the same height on the back seam as a fastening. Alternatively, simply leave the seam partially open and rely on the stretch to hold the cosy on.