Heres the fabric you will need..
25 cm lining
30 cm fabric
10 cm iron on interfacing
20 cm length of elastic

Measure a triangle 1/6 the circumference of the baby's head 1 1cm ease, by 8 22 .
add 1 cm Seam allowance on edges, and a curved allowance of 1.5 at the bottom edge

make a brim for front and back. these are half the circumference of the head each. I have drawn mine on the fold, so what you can see is half the final brim.
cut 6 x triangle in fabric
cut 6 x triangle in lining

cut 2 x each brim in fabric, and 1 x each brim in interfacing, which is trimmed back.
iron on interfacing.
Sew and notch brim on the curved edge

sew triangles together, and trim back at the top

sew across top of peak

trim back

Do the same with ling, but leave a gap to turn hat through later
press seams open.

Attach brim to fabric, centre front point of hat to CF point of brim, and Centre back point of hat to CB of brim

...

sew around, seams facing with 5mm seam

Ta Da

attach lining to hat by matching seams and sewing again around the edge, this time at a 1.5 seam allowance

Sew a channel slightly wider than the width of your elastic, and tread the elastic through by using a saftey pin

Try on baby. make sure it is firm, but not too tight. sew elastic down by sewing through all layers along the seam line.

Inside..sew up the gap, and your good to go..

CUTE!

you can also sew the peak down with a big button if you prefer..

and then it looks like this..