All basil flowers are edible.

You can eat them but if the flower buds have opened the stalk will be woody. Even chopping in a blender will make a stringy, unappealing product. So harvest all the buds you can along with the tender tip section that breaks off with a snap (no string) before the flowers open.

I strip the flowers off the stem and use them for garnish. The flowers taste better when they first open. They look very pretty and might even enhance one's appetite. I am heading toward my kitchen now. ;-]