Pattern:

Mohair yarn, in two colors. I used leftovers from the Colinette Absolutely Fabulous throw kit.
1 #17 circular needle (or straights)
1 #13 circular needle (or straights)
2 #7 (or similar small size) dpns
One button, at least one inch in diameter
Tapestry needle

gauge - not crucial

to fit just about anyone:

Collar:
Using the size 13 needle(s), cast on 45 stitches.
Work in seed stitch for about two inches.

Body:
Using size 17 needle(s):
Row 1: k6, yo, place marker (pm), k6, yo, pm, k21, pm, yo, k6, pm, yo, k6
Row 2: purl across
Row 3: k to marker, yo, slip marker, k to marker, yo, slip marker, k to marker, slip marker, yo, k to marker, slip marker, yo, k to end
Row 4: purl across
Repeat rows 3 and 4 until cape body is 2 inches less than desired length. The body in picture is 13 inches long.

Border:
Switch back to the size 13 needle(s) and work in seed stitch for two inches. Bind off very loosely.

Button and loop:
Sew button to one edge of the cape collar. I used a 1.5 inch mother of pearl button.
Using dpns, pick up three stitches at the edge of the collar. Work in i-cord to a length that will fit around your chosen button.

Weave in all ends and block aggressively.