This is a cute little bonnet, the second design in the Precious Hearts collection.
Worked flat in one piece, there is very little finishing to do.
There is an optional crocheted picot edge around the face and an eyelet row at the neck for a ribbon tie.
I used Cherub DK and Size 4 but I think the Cherub is more like a sport wt, so a thicker yarn will give you a medium size if you are looking for a larger version.