01 - Line an 8-inch square baking pan with parchment paper, leaving 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 smooth and melted. Remove from heat and stir in 1 teaspoon vanilla extract.
03 - Pour the chocolate mixture evenly into the prepared pan and spread to cover the bottom.
04 - In a mixing bowl, blend peanut butter, sifted powdered sugar, melted butter, sea salt, and 1 teaspoon vanilla extract until smooth and creamy.
05 - Gently spread the peanut butter mixture over the chocolate layer, smoothing the surface with a spatula.
06 - Refrigerate for a minimum of 2 hours, or until firm to the touch.
07 - Lift fudge out using parchment overhang and cut into 36 equal squares with a sharp knife.
08 - Store pieces in an airtight container in the refrigerator for up to one week.