Output audio to both HDMI and 3.5mm jack

OS: Debian Stretch

I would like to have audio output to both HDMI and 3.5mm jack for portability. That way I have the option of using one or the other depending on whatever system I need to plug into withing the need to change the config. If this is not possible then what is the best way to choose between the two. Right not, I have mopidy configured to use puleaudio and then I have to configure pulseaudio to use the correct sink. Not a big deal but definitely a little cumbersome. GStreamer seems able to do this using a tee statement but I have zero experience with it and I am a little lost.
Any assistance is very aappreciated.

I am using the mopidy config for puleaudio from here: https://docs.mopidy.com/en/latest/service/

Do you mean you want to output to one or the other, not both at the same time?
Doesn’t selecting auto in the audio raspi-config settings do what you want?
You would need to reboot, but if using it for portability then you would have unplugged anyway.

I may be remembering this wrong but I don’t think you have to reboot when switching between the audio jack and hdmi as I think it’s only changing the default device. I’m struggling to remember but I think I used to use both bits of hardware at the same time with my media setup. However, they recently changed the audio output driver a lot and I don’t know if you can still use both outputs simultaneously. Just do a quick experiment with gst-launch and use the sink parameters to specify the devices. Either run it in two shells or use a tee. I really should know this but I can’t remember!