How to copy a Mask Path into a Shape Path in After Effects

I always forget this...

Select the Layer containing the Mask
Hit "M" on the keyboard to reveal the Mask, or expand Mask > Mask
Click on the Mask Path with the Hourglass next to it and Copy
Select or create the Shape Layer
Select the Pen Tool and draw any kind of shape, this will create a new Shape/Path within the Shape layer
Expand Content > Shape > Path1 > Path to reveal the Path with the Hourglass next to it.
Paste the Mask Path into this newly created Path. Voilà!

The trick is to Copy / Paste the actual keyframes from the Mask Path to the Shape Path. The Path is actually buried one step below what you expect. You have to see the Hourglass to copy the keyframes, else you only copy the Mask from Layer 1 to a new Mask on Layer 2.