The beauty of knitting hats from the top down is that gauge doesn't matter; just try the piece on the wearer as you knit, and knit more or fewer rounds as appropriate.
Yarn: Lion Brand Cotton-Ease, 1/2 skein or less.
Needles: 5mm (US #8) needles for knitting in the round (I used 2 circulars)
Gauge: 4.75 sts / 1" (but see comment above)
Size: fits 6 month old (ditto)
Note: M1 = make one using Elizabeth Zimmermann's backward loop method.
CO 9 sts using wrap (aka figure 8) method as follows: wrap 6 loops around needles and K6 around. Then, K1, Kb&f around to complete the cast-on. (9 sts)
Rnd 1: *K1, Kb&f, Kb&f, repeat from * around. (15 sts)
Rnd 2: *K2tog, K1, Kb&f, M1, P1, repeat from * around. (18 sts)
Rnd 3: *K2tog, K2, Kb&f, M1, P1, repeat from * around. (21 sts)
Rnd 4: *K2tog, K3, Kb&f, M1, P1, repeat from * around. (24 sts)
Rnd 5: *K2tog, K4, Kb&f, M1, P1, repeat from * around. (27 sts)
Rnd 6: *K2tog, K5, Kb&f, M1, P1, repeat from * around. (30 sts)
Rnd 7: *K2tog, K6, Kb&f, M1, P1, repeat from * around. (33 sts)
Rnd 8: *K2tog, K7, Kb&f, M1, P1, repeat from * around. (36 sts)
Rnd 9: *K2tog, K8, Kb&f, M1, P1, repeat from * around. (39 sts)
Rnd 10: *K2tog, K9, Kb&f, M1, P1, repeat from * around. (42 sts)
Rnd 11: *K2tog, K10, Kb&f, M1, P1, repeat from * around. (45 sts)
Rnd 12: *K2tog, K11, Kb&f, M1, P1, repeat from * around. (48 sts)
Rnd 13: *K2tog, K12, Kb&f, M1, P1, repeat from * around. (51 sts)
Rnd 14: *K2tog, K13, Kb&f, M1, P1, repeat from * around. (54 sts)
Rnd 15: *K2tog, K14, Kb&f, M1, P1, repeat from * around. (57 sts)
Rnd 16: *K2tog, K15, Kb&f, M1, P1, repeat from * around. (60 sts)
Rnd 17: *K2tog, K16, Kb&f, M1, P1, repeat from * around. (63 sts)
Rnd 18: *K2tog, K17, Kb&f, M1, P1, repeat from * around. (66 sts)
Rnd 19: *K2tog, K18, Kb&f, M1, P1, repeat from * around. (69 sts)
Rnd 20: *K2tog, K19, Kb&f, M1, P1, repeat from * around. (72 sts)
Rnd 21: *K2tog, K20, Kb&f, M1, P1, repeat from * around. (75 sts)
Rnd 22: *K2tog, K21, Kb&f, M1, P1, repeat from * around. (78 sts)
Knit straight as follows:
Rnd 23: *K2tog, K23, , M1, P1, repeat from * around.
Repeat Rnd 23 until piece is 6" from cast-on point.
Next round, decrease as follows: *K2tog, K1, repeat from * around. (This mirrors EZ's original pattern, which is knit from the bottom up and, after the garter-stitch band, increases the number of stitches by 50%.)
Garter stitch band:
P 1 round.
K 1 round.
P 1 round.
K 1 round.
P 1 round.
K 1 round.
BO using purl decrease bind-off (which works well here because it's stretchy but not too stretchy): *P2tog, P2tog, slip 1st st on the right-hand needle over the 2nd st, repeat from * around.
(To avoid the step you get when binding off circular knitting, see
this lovely tutorial.)
The pattern for the original version is published
here.