It is a panel moulding, they make many profiles. There are a lot of sites you can purchase from, relatively inexpensive. Because you have a finished ceiling and you are only going to hit joist or rafters above you get an epoxy to assist in attachment to ceiling. They also have the premade corners in different styles as well. Good luck!

Thank you so much for answering my question I appreciate it what size is your panel molding by chance

Been a while since that project. Want to say it was 2"-2-1/4" width??? Think I got it at Architectural Depot, look under panel moulding and they have lots of choices.

Thank you again for all of your help that actually is the website that I was actually looking on to buy my molding from. Take care