Line an 8x8 or 9x9 inch baking pan with parchment paper, leaving a little overhang on each side. Set aside.
Add together the vanilla frosting and peanut butter chocolate spread in a microwave safe bowl. Do not mix. Microwave on high for 1 minute. Stir until well combined and smooth. Pour into the prepared pan and spread out evenly. Top with the Reese's Pieces, pressing the candy into the top of the fudge. Refrigerate until firm (about 1-2 hours).
Remove the fudge from the pan using the parchment paper. Set the fudge on a cutting board and remove the parchment paper. Allow the fudge to come to room temperature for at least 15-20 minutes (the fudge will cut more evenly then). Cut into 12 even squares.