SSL connection to Proxy Servers

Hi,

It would be nice if Firefox would be able to CONNECT
to Forward Proxy Servers trough an encrypted SSL channel.

Browser < -SSL-> Squid Forward Proxy

As fas as I know none of the browsers has that.
I'm not talking about proxying https traffic but rather
making all the connection to the proxy server through https.
This is vital for clients authenticating to the proxy server
(basic auth over SSL) as well as hiding sensitive personal
information like URLs visited. I would also be nice to support
(mutual?) proxy authentication with SSL client certificates.

Best Regards,

Giannis