Preheat oven to 350°. Line a 9x13 cake pan with foil and spray with non stick cooking spray. Set pan aside.
In a medium sized bowl, whisk together flour, baking soda, and salt and set aside.
In the bowl of a stand mixer, or in a large bowl with a hand mixer, beat butter and sugars together until fluffy. Add eggs one at a time and continue to mix until well combined. Add vanilla extract.
With mixer on low speed, slowly add flour mixture to bowl and mix until combined scraping sides of bowl as needed. Stir in chocolate chips.
Transfer cookie dough to lined cake pan and sprinkle with additional mini semi sweet chocolate chips and milk chocolate chips. Bake for about 30 minutes, until cookies bars are light golden brown. Do not over bake.