Instructions

• Preheat the oven to 350°F (180°C) or 160°C for a fan oven. Grease and line a 9×13-inch (approx. 23×33 cm) baking pan with parchment paper, leaving some overhang for easy removal.
• In a large bowl, whisk together the melted and cooled ½ cup (113 g) unsalted butter, 1 cup (200 g) granulated sugar, and ¾ cup (150 g) light brown sugar until smooth.
• Add 3 large eggs, 1 teaspoon (5 ml) pure vanilla extract, and ½ teaspoon salt to the butter-sugar mixture. Whisk until fully combined.
• Add ¾ cup (60 g) cocoa powder and ¾ cup (90 g) all-purpose flour. Stir with a spatula or spoon until no dry streaks remain and the batter is uniform.
• Pour the batter into the prepared pan and smooth the top into an even layer. Bake in the preheated oven for 18–20 minutes, or until a toothpick inserted near the center comes out with a few moist crumbs.
• Remove the brownies from the oven and let them cool completely in the pan on a wire rack.
• While the brownies cool, make the peanut butter layer: in a medium microwave-safe bowl combine 1½ cups (360 g) smooth peanut butter and ½ cup (113 g) unsalted butter. Microwave in 30-second intervals, stirring well after each interval, until the mixture is smooth and pourable.
• Add 2½ cups (300 g) powdered sugar to the peanut butter mixture and mix until combined; the mixture will be stiff. Add 1–2 tablespoons milk, a little at a time, until the mixture becomes smooth and spreadable.
• Spread the peanut butter mixture evenly over the cooled brownies, smoothing to the edges.
• Make the ganache: heat ¾ cup (180 ml) heavy cream until steaming (do not let it boil). Pour the hot cream over 1½ cups (255 g) semi-sweet chocolate chips in a heatproof bowl and let sit for 3 minutes. Stir until the chocolate is fully melted and the mixture is smooth.
• Pour and spread the ganache evenly over the peanut butter layer. Refrigerate for at least 1 hour to set before using the parchment overhang to lift the slab from the pan and slice.