Preheat the oven to 350F. Line a 8 x 8 pan with parchment paper and set aside.
Add the butter to a microwave safe bowl. Melt in the microwave.
Add sugar to the melted butter, stir to combine. Place in the microwave for 30 seconds. Stir. Place in the microwave for 60 more seconds until the mixture is bubbling.
Add the 4 ounces of chocolate into the mixture, stir. The chocolate should melt right away, if it is still lumpy, place back into the microwave until everything is well incorporated.
Add the eggs to the bowl. Whisk until the mixture looks smooth.
Add the vanilla, salt, flour, and cocoa powder. Mix everything together.
Fold in the baking chips.