I have cpanel and WHM and was curious if there is anyway to have an email delivered to an inbox and at the same time forward that to another address. Is this possible with the mail built into cpanel?

In cpanel
click mail
click forwarders
click add forwarders
fill in the blanks
click add forwarder
DONE

will this still leave a copy on the server before forwarding?

Yes
as long as the from address is an email account.

e.g.
me@mydomain.com is an email account
forward to me@hotmail.com
email will be delivered to me@mydomain.com and a copy will be forwarded to me@hotmail.com

I did this and it only forwards the email and does not deliver a copy locally.

If you forwarded emails that are to be delivered to me@mydomain.com to me@hotmail.com.

To have a copy stay in server, me@mydomain.com must be an email account in cpanel.