Totally accidentally shilling for SE right now, but I learned a bunch of really cool tricks for cookies from an analysis about the different variables in cookies [1] that basically let me basically "build" my own secret recipe. Stuff like browning the butter before mixing it into the dough, resting dough overnight, using precise mixes of egg/flour, using chopped chocolate instead of chips, etc.

[1] https://sweets.seriouseats.com/2013/12/the-food-lab-the-best...