Preheat oven to 350 degrees.
Line a 9x13 baking dish with foil, leave some overhang to make removal easier.
Spray foil generously with nonstick cooking spray.
In the bowl of a stand mixer, beat butter, granulated sugar, and brown sugar together until fluffy.
Add in eggs and vanilla extract and continue to beat.
Lower speed of mixer and add flour, baking soda and salt, and mix until combined.
Add 1 cup of chocolate chunks and 1 cup of mini chocolate chips and give a final stir, reserving some chocolate chunks and mini chocolate chips for topping cookie bars.
Transfer cookie dough to prepared baking dish.
Press remaining chocolate chunks and a sprinkle of mini chocolate chips into top of cookie dough.
Bake 30 minutes on middle rack of oven. Adjust baking time as needed but don't over bake. Top should be a light golden brown and middle of cookie bars will still still be soft. Cookie bars will continue to bake and set as they cool.
Let cool completely and cut. Store tightly covered to keep soft.