This was designed for the Knitmore Girls’ preemie hat contest, which asked for hats sized for premature babies that could be made with leftover sock yarn. The yarn used here was Red Heart Heart & Sole in Watercolor Stripe, but any yarn can be used; in fact, I think this hat could be made to any size by following the same proportions: knit the I-cord brim to fit, increase the stitches by 1/3 (k2, YO) to make the body of the hat, knit until the body of the hat is 2/3 as long as you want it, then decrease as in the pattern to 6 stitches and close off the top of the hat. Use needles appropriate to your yarn.
15 grams (75 yards) fingering weight yarn
US2 and US3 double-pointed needles
With a provisional cast on (use your favorite method), cast 2 stitches onto US2 needles. Leave a generous tail of yarn for finishing the hat.
Knit 2-stitch I-cord for about an inch, or long enough to loop around your little finger. Undo your provisional cast on and put the freed stitches onto the dpn so that the I-cord makes a loop.
Knit across all stitches to make a 4-stitch I-cord. Knit the I-cord long enough to make the brim of the hat–I-cord only has a little stretch, so measure for a fit with no or little negative ease.
When the I-cord is long enough , knit two stitches together (k2tog) twice, to leave 2 stitches on the needle. Pull the working yarn back to the right end of your needle (as you’ve been doing to make the I-cord) and k2tog to leave 1 stitch on the needle.
Leaving the stitch on your needle, pick up and knit every stitch on the length of your I-cord with the US2 needles. Stop when you reach the loop on the end. Purl back.
Over 3 US3 dpns, *knit 2, YO* until you reach the end of the I-cord (nothing bad will happen if you have to fudge a stitch or two at the end). Join the stitches in the round and knit stockinette stitch for two inches (2/3 the total desired length of the hat) from the picked up stitches on the I-cord.
Place a marker opposite the loop to mark the back of the hat, and start the decrease rounds: *k2, k2tog* for one round, knit one round plain. Continue these rows until you have about 24-30 stitches. Begin *k2tog* until you have 6-8 stitches. Break the yarn, leaving a tail, and use it to close up the top of the hat.
Weave in ends. With the tail of the cast on, stitch the end of the I-cord to the base of the I-cord loop. Position the button so the shank is inside the loop and sew it in place.
The button is optional: just make the i-cord without the loop.