Screen mirroring

So I go into the control centre on my MacBook Pro and choose Screen Mirroring.

I get options for my connected devices.

I choose the one I've called, Living Room, which is my Apple TV.

I get the option to "Mirror-Built-in Retina Display", or "Use as Separate Display".

I choose "Mirror-Built-in Retina Display".

My MacBook Pro's screen is now on my Living Room TV.

Excellent. Just what I wanted.

Later, I want to stop mirroring my MacBook Pro on my TV.

I go to the Control Centre on my MacBook Pro, click on Screen Mirroring, expecting to see an option that says something like, Stop Mirroring...

But there is no such option. I can change it to "Use as Separate Display" if I want, but not turn it off completely.

How do I get my TV screen back to just being a TV screen, and my MacBook Pro's screen to just being on my MacBook Pro?

If there is an option to turn something on in the Control Centre, surely there'd be an option to turn it off in the same place, right?

Very frustrating.