Q: Apple Tv mirror + Airport Express audio output = How to?

I want to mirror my MacBook to the Apple Tv but I want to send the audio to the Airport Express.
If I ask my Apple Tv to send the output to the Airport, it works just fine.

If, after that, I use the iPhone to mirror the screen and watch some video on youtube or Twitch, it works fine either.
But if I use my MacBook Pro to mirror the screen, the audio output is sent to my TV through the HDMI cord.

Is that any way that I can solve this?
What I want to do is just mirror my MacBook screen with the audio coming out through the Airport Speaker.

Thanks for any help, folks!