Preheat oven to 350°F, line a 8x8 square pan with parchment paper, spray with cooking spray and set aside.
Sift together flour, cocoa powder and salt in a bowl and set aside.
Melt butter and chocolate chips over water bath or in microwave (in 30 sec increments) until completely melted
In your mixing bowl add both sugars and eggs and mix on med-high for 5 mins to get light and fluffy.
Add the butter and chocolate mixture and vanilla to bowl and mix.
With mixer on low add your dry ingredients until just combined.
Finally fold in chocolate chips if your adding them (or any other add ins, walnuts, candy....)
Pour into prepared pan and bake in oven for about 35 mins (I like mine under done so usually take them out at the 30 min mark they keep cooking with residual heat of pan while cooling).
Cool in pan for 20 mins and transfer onto a cooling rack to cool completely (another 30 mins) before cutting into them.
Notes
When measuring flour make sure you spoon level it for accuracy. More flour leads to a cakey brownie.