01 - Line an 8x8-inch square baking pan with parchment paper, allowing overhang on opposite sides for easy removal of the fudge later.
02 - In a medium saucepan over low heat, combine chocolate chips, sweetened condensed milk, and 2 tablespoons butter. Stir constantly until completely melted and smooth. Remove from heat and mix in 1 teaspoon vanilla extract.
03 - Pour half of the chocolate mixture into the prepared pan. Use an offset spatula to spread evenly across the bottom. Freeze for 10 minutes until just set.
04 - In a separate saucepan over low heat, melt peanut butter and 1/2 cup butter, stirring until smooth. Remove from heat. Whisk in vanilla extract, salt, and powdered sugar until creamy and well combined.
05 - Spread the peanut butter mixture evenly over the chilled chocolate layer, working quickly while the base is still firm.
06 - Pour the remaining chocolate mixture over the peanut butter layer. Smooth the top with a spatula for an even finish.
07 - Refrigerate for at least 2 hours or until completely firm throughout.
08 - Using the parchment overhang, lift the fudge from the pan. Cut into 24 equal squares. Serve chilled or at room temperature.