01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - Whisk melted butter and sugar in a large bowl until smooth. Add eggs and vanilla; whisk until well combined. Sift in cocoa powder, flour, and salt. Mix until just combined—do not overmix.
03 - Spread batter evenly into prepared pan. Bake for 22–25 minutes until a toothpick inserted in center comes out with moist crumbs. Cool completely in pan.
04 - Beat peanut butter, melted butter, powdered sugar, vanilla, and salt in a medium bowl until smooth and creamy. Spread evenly over cooled brownie base. Refrigerate 30 minutes to set.
05 - Place chocolate chips in a heatproof bowl. Heat heavy cream until just simmering, then pour over chocolate. Let sit 2 minutes, then stir until smooth. Cool slightly, then pour and spread over peanut butter layer.
06 - Refrigerate at least 1 hour until set. Lift brownies from pan using parchment overhang. Cut into squares and serve.