i wonder why would u even mention about transfer to your current employer. Give them your 2 weeks notice after your transfer have been completed. The only thing u need from them is your recepit number. Each time u apply for your H1 transfer/new one you are electronically checked for your previous H1B approval for which your receipt number ( WAC or EAC number ) is enough, though it;s good to provide them with the photocopy of your H1B approval. In addition to that u don;t even need to wait for approval as soon as u apply for H1b for new company u can work for them.
http://www.h1base.com/visa/work/H1B%20Visa%20Transfer%20To%20A%20New%20Employer/ref/1169/