Preheat oven to 350 degrees Fahrenheit. Line an 8x8 inch square pan with parchment paper.
To make the cookie bars:
Cream together butter and sugar until soft and fluffy.
Add eggs and vanilla; mix until thoroughly incorporated.
Add the flour, salt and baking soda. Mix again just until combined, scraping the side of the bowl as needed.
Stir in chocolate chips.
Evenly press dough into prepared pan.
Bake cookie bars until edges begin to golden, about 30 minutes.
Remove from oven and cool completely.
To make the frosting:
Cream together cream cheese and butter.
Add cocoa powder and ½ of the powdered sugar. Mix on low until combined.
With mixer running on low, add remaining powdered sugar, vanilla, and milk.
Once all the ingredients have been added, increase mixer speed to medium high and beat until frosting is light and airy, about 4 minutes.
Evenly spread cookie bars with frosting and garnish with additional chocolate chips, if desired.
Slice and serve immediately or refrigerate until ready to serve.
The calories shown are based on the bars being cut into 16 pieces, with 1 serving being 1 frosted bar. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**