Preheat the oven to 350 degrees Fahrenheit. Spray an 8x8 square pan with cooking spray and line the pan with parchment paper leaving a slight overhang.
To a medium bowl add flour, salt, and cocoa powder. Whisk to combine and set aside.
In a large bowl set over a small saucepan half filled with simmering water, add the chocolate and butter. Stirring occasionally, allow the butter and chocolate to melt completely. Turn off the heat and remove the bowl from the pot of simmering water. Add the granulated and brown sugars and whisk to completely combine. Set aside and allow the mixture to come to room temperature.
Add 3 eggs to the chocolate/sugar mixture and whisk until the eggs are combined. Add the remaining eggs (2) and whisk until combined. Stir in the vanilla, but be sure NOT to over whisk at this stage. Otherwise this will change the texture of your brownie.
Sprinkle the flour mixture over the chocolate mixture and with a rubber spatula, fold until somewhat combined, but you can still see large bits of flour. Add the chocolate chips* and fold until mostly combined. You should still see small bits of four remain in the batter.
Pour half the batter into the pan and add the peanut butter filling by the spoonful. It doesn’t have to be uniform, just dollop that situation. Pour the remaining batter over the peanut butter filling and smooth with an offset spatula. If you see bits of peanut butter filling, that’s cool.
Place in the oven and bake for 43-45 minutes, rotating the pan midway through baking. What you’re looking for is the edges to be set, yet the middle to jiggle when the pan is moved. Don’t worry, they will set.
Remove from the oven and allow the brownies to cool for at least 4-5 hours before cutting. Lift from the pan, cut into squares (large or small) and serve. Note – The brownies will be very gooey. And you’re going to dig that. Serve alone or top that situation with some ice cream.
Store at room temperature in an airtight container or wrap with plastic wrap for up to 3 days.
Makes 9 large brownies, 18 smaller brownies