In a medium bowl, mix the flour, baking soda, and salt. Set aside.
In another bowl, using mixer, beat the butter, peanut butter, and sugars, until smooth and fluffy.
Add egg and vanilla extract and combine until mixed.
Gradually add the flour mixture into the wet mixture mixing well after each addition.
Cream cheese filling: In a medium bowl, beat together the cream cheese, egg, powdered sugar, and vanilla until smooth.
Spread ⅔ of the cookie dough in the bottom of the 8-inch baking dish.
Add one half of the Reese's cup, chopped on top of cookie dough.