Set your oven to 350°F. While it warms up, line a 9x13-inch baking pan with parchment paper, letting the edges hang over for easy removal later.

In a large heatproof bowl, melt together unsalted butter and semi-sweet chocolate chips in the microwave. Microwave for 30 seconds at a time, stirring in between, until fully smooth. Once melted, let it cool slightly, then whisk in granulated sugar, light brown sugar, and vanilla extract. 

Whisk in the eggs one by one, mixing after each. Fold in cocoa powder, flour, and salt. If you like, add instant espresso powder for an extra punch of chocolate flavor.

Transfer the brownie batter to the prepared pan, spreading it in an even layer. Bake for 30 minutes, or until a toothpick shows a few moist crumbs. Cool the brownies in the pan until fully set.

Beat the butter until fluffy, then add the peanut butter. Slowly mix in the powdered sugar, one cup at a time, until smooth. Taste and adjust sweetness if needed.

Spread this peanut butter layer evenly over the cooled brownies. Press it down gently, then refrigerate for about 20 minutes to firm it up.

In a heatproof bowl, place semi-sweet chocolate chips. Heat the cream until it’s just about to boil, then pour it over the chocolate chips to blend. Wait for 4 minutes, then mix until it’s smooth and easy to pour.

Pour the chocolate ganache over the peanut butter layer and spread it evenly. Chill for 30 minutes until set. Lift with parchment, slice, and enjoy!