Preheat the oven to 350 degrees and spray a 9 inch pie dish or pan with non-stick cooking spray and set aside.
In a medium bowl, sift together the flour, baking soda, cornstarch, and salt and set aside.
Using a mixer, beat together the sugars and melted butter on medium speed until well combined.
Add in the egg, egg yolk, and vanilla extract until well combined.
Gradually add in dry ingredients into the butter/sugar mixture until well combined.
Using a large wooden spoon, fold in the all the chocolate chips until just combined.
Transfer the batter out into the prepared pie dish and smooth out the top.
Evenly space out the 8 Mini Reese’s Peanut Butter Cups around the cookie pie edge about an inch in from the edge and lightly push them in, with tops still exposed. If you are adding more cups, just add them within the circle of cups.
Bake for 25 minutes.
Allow the cookie pie to cool completely before frosting. (If you are not frosting, just add your sprinkles to the top as desired. If you want to just do a frosting border instead of doing the frosting the whole pie, just halve the frosting measurements.)