Screen sharing - two monitors

I have 2 monitors attached to my Sierra laptop and I screen share into a headless Mini running Monterey.

Ideally I’d like the Mini to use two screens at times but can’t figure out how. I read that one can open a second session, and I do see the “New Connection” under the Connection menu, but I can’t figure out the syntax that would connect to the Mini that way.

I’ve also tried this going from the Mini to another machine so it doesn’t seem to be something that’s changed in a newer OS.

Does anyone know for sure?