01 - Line an 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - Combine chocolate chips, 1/2 cup sweetened condensed milk, and 1 tablespoon butter in a heatproof bowl. Melt using a double boiler or microwave in 20-second intervals, stirring until smooth. Stir in 1/2 teaspoon vanilla extract.
03 - Pour the chocolate mixture into the prepared pan and smooth the surface evenly. Refrigerate for 20 to 30 minutes until slightly firm.
04 - In a separate bowl, combine peanut butter, 1/4 cup sweetened condensed milk, 1 tablespoon butter, and salt. Heat gently in the microwave for 30 to 40 seconds or on the stovetop, stirring until smooth. Stir in 1/2 teaspoon vanilla extract.
05 - Spread the peanut butter mixture evenly over the chilled chocolate layer.
06 - Refrigerate for at least 2 hours or until fully set.
07 - Lift the set fudge from the pan using the parchment overhang and cut into 16 squares. Store in an airtight container in the refrigerator.