I cut a bigger circle than the brim from velvet, and from another fabric as well. I basted the edge twice to gain nice smooth gathering. Then I found out the circle was too big (grrr). Basted again (and then cut along the smaller basting).
I marked eight leading points on both the brim and the circle and joined them with my favourite method - I joined them with one pin, then I did it with the pins on the opposite side, then I searched for the middle ones and so on. I tightened the basting.
Sewing (somewhere between the two gathering cords) was quite uncomfortable as I let there an amount of space at the lower layer of the brim. It will serve me when I want to finish the beret - there are still rough seams inside.
The one at the right is a small model I'd made. The dog doesn't seem to like the beret..
I was right taking the work to the bus, the rest was sluggish.. I cut the inner gathered fabric to exceed only with a few milimeters. I also cut the big black part I'd left inside the ring, but about two centimeters from stitches. I folded it around the gathering and attached with my nice rice stitch (still don't know the right name :-D ). Before fastening of every stitch I tightened the previous one and helped the velvet and eventual threads disappear inside with my scissors. This way I gained a good quality inner seam.
Unfortunately, this seam (just about half a cm) made the perimeter four centimeters smaller! which I hadn't expect as I'm not good at maths. Although the beret turned out OK it's quite tight. Next time must be better:)