The pattern is by Woolly Wormhead, and is available as a free Ravelry download.
The pattern calls for worsted weight yarn and uses one and a bit balls. Very quick and easy to make. It's supposed to be knitted in the round but I did my usual of adapting it to straight needles.
I love the colour of this hat and it is very easy to wear.
The pattern gives options for variations on the beret. I chose to make the slouchy version with a rolled and ribbed brim. Full detials of the yarn etc I used can be seen on my Ravelry page here.