01 - Preheat oven to 350°F. Line 8x8-inch baking pan with parchment paper, leaving overhang for easy removal.
02 - Whisk melted butter and sugar until smooth. Add eggs and vanilla; whisk well. Sift in cocoa powder, flour, and salt. Mix until just combined.
03 - Spread batter evenly in prepared pan. Bake 22-25 minutes until toothpick inserted comes out with moist crumbs. Cool completely in pan.
04 - Beat peanut butter, melted butter, powdered sugar, vanilla, and salt until smooth and creamy. Spread evenly over cooled brownies. Refrigerate 30 minutes to set.
05 - Place chocolate chips in heatproof bowl. Heat heavy cream until simmering, pour over chocolate. Let sit 2 minutes, stir until smooth. Cool slightly.
06 - Pour and spread ganache over peanut butter layer. Refrigerate at least 1 hour until set. Lift from pan using parchment. Cut into squares and serve.