What type of disc did you "format"? For now I will assume DVD disc.
After you did this formatting, did you get a message that the disc was reusable after this formatting?
If you really did do a Full Erase of the DVD-RW, you should be able to do a burn to disc DVD.
If you did an incomplete erase or if there was content on the DVD-RW at the time of burn to disc DVD, you should get a message asking if you want an erase of the content so that a burn to disc can take place.
There is no multisession feature in burn to disc DVD if that is what you are looking for.
Please review and please give full details, including version of Premiere Elements used and on what computer operating system it is running. For now I have assumed that you are running some version of Premiere Elements on some version/edition of Windows.
As a test... direct your DVD output to a folder on your hard drive, instead of direct to disc
Then, use the FREE http://www.imgburn.com/index.php?act=download to write your folder to disc (send the author a PayPal donation if you like his program)
Read http://forums.adobe.com/thread/1322583 for notes on installing Imgburn WITHOUT any toolbar add-ons