01 - Line an 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a medium saucepan over low heat, combine chocolate chips, sweetened condensed milk, and 2 tablespoons butter. Stir continuously until melted and smooth. Remove from heat and stir in 1 teaspoon vanilla extract.
03 - Pour the chocolate mixture into the prepared pan and spread evenly.
04 - In a separate bowl, combine peanut butter, powdered sugar, melted butter, sea salt, and 1 teaspoon vanilla extract. Stir until smooth and creamy.
05 - Gently spread the peanut butter mixture over the chocolate layer, smoothing the surface with a spatula.
06 - Refrigerate for at least 2 hours, or until firm.
07 - Use parchment overhang to lift fudge from the pan. Cut into 36 small squares with a sharp knife.
08 - Place fudge pieces in an airtight container and refrigerate for up to one week.