Line a 8x8 baking dish (for thick brownies) or a 9x13 baking pan (for thinner, crispier brownies) with parchment paper and spritz with non-stick cooking spray.
In a microwave safe bowl, combine chocolate chips, butter, and peanut butter.
Heat in the microwave for about 1 minute, stopping to stir vigorously every 30 seconds until smooth. Be careful not to overheat or burn the chocolate mixture.
Add the sugar, cocoa powder, and salt to the bowl and stir to combine.
In a separate bowl, whisk eggs together with vanilla. Pour the egg mixture into the chocolate batter and stir until well combined.
Transfer batter to prepared baking dish and spread out evenly.
Bake in a 8x8 baking dish for 35 to 40 minutes or in a 9x13 baking dish for 30 to 35 minutes.
Remove brownies from oven when they are cooked through but still slightly soft in the middle. Allow to cool completely in the pan before slicing.
Lift the brownies from the baking dish with the parchment paper and cut into squares, cleaning the knife between slices. Enjoy!