Been working with the Large Cochins for years and yes they are very broody!!! However, I only use them to set duck and goose eggs because they tend to break chicken eggs due to their weight. I do not recommend them for setting chicken eggs. If you are looking for a good broody bird that will set several eggs and be a good setter as well as mother I would recommend Sumatra hens, they will set for ever and are very good mothers. I used Sumatra hens as incubators before I bought cabinet incubators and one hen set for over 60 days straight, I hatched three clutches of eggs from her.
Bo Garrett