To be honest, I'm not sure I'm understanding your request, but I connect my laptop to my TV often via HDMI. Basically, all I have to do is connect it. However, if I want to get fancy, I can press one of the function keys on laptop to decide if the second screen (TV) duplicates the laptop screen, or is a second (different) screen, or if the laptop screen should turn off. (One of those options may be to disable the HDMI entirely so you would want to make sure that isn't set.)
I've never thought of this in terms of casting or mirroring, but rather just "video out".
Of course, the TV needs to be set to whatever input is connected.
