Preheat your oven to 350 degrees and grease or spray a 9 x 13 baking pan. Set aside.
Using a large, heat-safe bowl placed on top of a pan of simmering water, melt the butter completely. Turn off and remove from the heat and mix in the cocoa and then the espresso powder until fully combined. Pour in the coffee and sugar and continue to stir until combined and smooth. Add in the eggs and vanilla and mix until fully combined.
In a separate bowl, combine the flour, baking soda and salt and then, pour the flour/dry mixture, slowly in three batches, into the wet mixture, mixing well after each addition until smooth. Pour in the slightly melted peanut butter and just swirl in. You still want to see some streaks of peanut butter. Then, pour in the chocolate chips and mix slightly.
Pour the brownie batter into prepared baking pan and bake for about 45 to 50 minutes. Remove from the oven and let cool for at least 30 minutes before cutting and serving. Enjoy!