Layer Mask or Mask Artwork Without Destroying Or Losing The Layer Using Clipping Mask?

I'd like to mask out part of a layer without damaging it or cutting out, as so when I make an after effects animation of making the eye empty at first when it opens (no pupil), then the eye (pupil) coming into to scene as if it were just waking up (pupil in the middle). How do I go about this without using a clipping mask and destroy the layer? Below are examples of the initial shape of eye and pupil asset id like to preserve (FIRST SCREENSHOT), Then is the desired effect I'd like to achieve for the finalized logo (SECOND SCREENSHOT). Any help would be appreciated. Do I follow this video?
https://www.youtube.com/watch?v=cWjrb1jWbtg&ab_channel=AlainParadis