01 - Line an 8-inch square baking pan with parchment paper, allowing overhang on opposite sides for easy removal.
02 - Combine peanut butter and butter in a medium saucepan over low heat. Stir continuously until melted and smooth, then remove from heat.
03 - Add powdered sugar, vanilla extract, and salt to the warm peanut butter mixture. Mix thoroughly until fully incorporated and creamy.
04 - Spread the peanut butter mixture evenly into the prepared pan. Use a spatula to create a smooth, level surface.
05 - Place chocolate chips and butter in a microwave-safe bowl. Microwave in 20-second intervals, stirring between each, until completely melted and smooth.
06 - Pour the melted chocolate over the peanut butter layer. Spread quickly and evenly before it begins to set.
07 - Refrigerate for at least 2 hours, or until completely firm throughout.
08 - Lift the fudge from the pan using the parchment paper handles. Cut into 16 equal squares. Serve chilled or allow to come to room temperature.