cochins are great mothers and go broody often! I have not personally tried this, but I've heard they will hatch any kind of egg, doesn't have to be a chicken! I have had one go broody and put some of my parents chicken eggs under her along with her own eggs and she hatched and took care of them!
My Cochins, standard and bantam, are superior setters and mamas. My Silkies can not even come close to being as good of broodies or mama hens. I can get 12 eggs under my standards without a problem and they will hatch and raise all the chicks without any fuss. The banties can easily set on 7 eggs and raise them very nicely.
My Silkies aren't smart enough to cover all the eggs or turn them well. Once they hatch the chicks they aren't quite sure what they should do and are often too rough on the poor chicks and have left them out crying in the rain too many times. I have many different bloodlines on my Silkies but have not been very impressed with their raising chicks ability.
I have several flocks of Cochins and they have never let me down.