@husterk:
Thanks for the tips… any chance I could make this work without needing to modify the Cisco ASA settings? I may not have access to this device.
I can't think how to do that - the Cisco needs to know somehow that the pfSense WAN IP is a gateway to 192.168.1.0/24
Your NAT solution is the standard way, essentially faking the pfSense LAN side address using a WAN side address that the Cisco is already happy to talk with.
By the way, if you do change the Cisco to add a route to 192.168.1.1 then you will have trouble when you VPN in to the Cisco from your favourite cafe/friend's house that is using 192.168.1.0/24 locally. If possible, I would change the LAN subnet to something less common - out of the 10.0.0.0/8 space or 172.16.0.0/12 space or down the end of 192.168.0.0/16.