Originally Posted by QuiltE

If you like the cookies you have, try adding an extra egg.
The egg will give you a softer texture, tending towards cake-like.

I do this all the time with several different cookie recipes.

The hardness could also be caused by a hotter oven and/or too long of a bake.

It's easy to over bake cookies, thinking they aren't quite baked,
and yet they really are ready to remove from the oven.
Then let sit on the cookie sheet for a while before transferring to a wire rack.