Instructions

• Line an 8"x8" pan with parchment paper or foil, leaving a 1–2 inch overhang on two opposite sides for lifting the fudge out later; set the prepared pan aside.
• Measure 3½ cups powdered sugar into a large bowl, sift it well, and set the sifted powdered sugar aside.
• In a heavy-bottomed saucepan set over medium heat, combine 1 cup unsalted butter, 1 cup creamy peanut butter, and ½ cup Reese’s peanut butter chips.
• Stir constantly with a heatproof spatula or spoon until the butter, peanut butter, and chips are fully melted and the mixture is completely smooth.
• Reduce the heat to low and stir in 1 tablespoon pure vanilla extract.
• Keeping the pan over low heat, add the sifted powdered sugar a cup at a time and stir thoroughly after each addition until fully incorporated and the mixture is smooth. If any lumps form or the mixture looks grainy, vigorously whisk or press the mixture against the bottom of the pan with the spatula to break up lumps.
• Stir in ½ teaspoon kosher salt, then add ¼ cup marshmallow creme and mix until the marshmallow creme is fully incorporated and the mixture is uniform.
• Transfer the fudge mixture to the prepared 8"x8" pan and use an offset spatula or the back of a spoon to spread it evenly and smooth the top.
• Refrigerate the pan uncovered for 1½ to 2 hours, or until the fudge is firm to the touch.
• When set, lift the fudge from the pan using the parchment/foil overhang and place it on a cutting board. Cut into squares as desired (for very small pieces, you can cut the 8"x8" pan into 64 pieces with 8 cuts in each direction).