01 - Line an 8-inch square baking pan with parchment paper, leaving some overhang for easy removal.
02 - In a medium saucepan over low heat, combine chocolate chips, sweetened condensed milk, and 2 tablespoons butter. Stir constantly until smooth and melted. Remove from heat and stir in 1 teaspoon vanilla extract.
03 - Pour half of the chocolate mixture into the prepared pan and spread evenly. Chill in the refrigerator for 10-15 minutes until slightly set.
04 - In a medium bowl, stir together peanut butter, powdered sugar, melted butter, and ½ teaspoon vanilla extract until smooth.
05 - Spread the peanut butter mixture evenly over the chilled chocolate layer.
06 - Pour the remaining chocolate mixture over the peanut butter layer and spread evenly.
07 - Refrigerate for at least 2 hours, or until fully set.
08 - Lift the fudge out using the parchment paper, cut into squares, and serve.