Preheat oven to 350F and grease or line an 8x8 baking pan with parchment paper
Melt the butter and chocolate chips together in the microwave or double boiler. Mix in the creamy peanut butter and vanilla extract.
In a separate bowl combine the eggs and sugar and mix with an electric mixer or whisk attachment for a stand mixer until light and fluffy - about 3 minutes.
Gently fold the melted chocolate mixture into the eggs and sugar with a flat spatula. Fold in the cocoa powder and salt.
Pour the batter into the lined pan and smooth into an even layer. Optional: Drizzle extra peanut butter over the top and mix with a toothpick to make a swirl effect.
Place in the oven and bake at 350F for 28 minutes.
Cool completely and then cut into squares
Notes
If your brownies always get stuck to your knife when you cut them try this tip. Use a plastic knife! Allow the brownies to cool completely and then use a plastic disposable knife to cut through them. Much less of the fudgy brownie batter will get stuck to a plastic knife.
If you like a very dark and rich brownie, use dark chocolate chips and dutch process cocoa powder. I don't recommend using brown sugar in place of the regular granulated sugar because it will increase the moisture content of the brownie batter.
Not a peanut butter fan? Swap out the peanut butter for any nut butter that you like These would be delicious with almond butter, cashew butter or even a hazelnut butter. There is a mixed nut and seed butter blend that I like to get at Trader Joe's that I think would be delicious when paired with chocolate.
Get a fudgier brownie depending on what peanut butter you use. You can use any peanut butter for these but Skippy and jif peanut butter both make for an extremely fudgy brownie.
Adjust salt depending on what peanut butter you use. If you use unsalted peanut butter, add an extra 1/4 tsp of salt.