Shoot a video in iPhone 7 Plus' Portrait mode

I need to shoot an interview with my iPhone 7 Plus, and I'd like it to have the beautiful bokeh effect (shallow depth of field) that the Portrait mode in the camera has. However, my iPhone only lets me take pictures in Portrait mode, not video.

One possible workaround is to record the built-in preview of Portrait Mode with QuickTime, which would work great except for the controls showing up, which cannot be cropped out.

Is there any way to record video in Portrait mode (or hide the controls from my iPhone's screen so I can record using QuickTime), or at least is there any other way to get the bokeh effect while recording a video from my iPhone?

Thank you in advance.

No, you cannot do this without a jailbreak.(unless you were doing stop motion).

The workaround you mentioned would work, though. How to crop a video(cropping the frame around the subject): https://filmora.wondershare.com/video-editing-tips/free-video-croppers.html

You can record the screen like this using Quicktime:(I don't have an iPhone7 so I don't have portrait mode):