Line an 8x8-inch baking pan with a piece of parchment paper. Cut the parchment paper a few inches too long on all sides so you can easily lift the fudge out of the pan once it hardens. Set the prepared pan to the side.
In a large saucepan set over medium, heat the sugar, butter, and evaporated milk, stirring until it melts together. Continue to stir the mixture until it begins to boil. It will begin to become foamy and bubbly.
3 cups granulated sugar, ¾ cup unsalted butter, 5 ounces evaporated milk
Continue stirring the fudge for an additional minute. Once done, remove it from the heat and stir in the peanut butter chips, chocolate chips, and marshmallow creme. Continue stirring the mixture until the chips have completely melted and mixed in with the marshmallow creme, about 1-2 minutes.
¾ cup peanut butter flavored baking chips, ¾ cup semisweet chocolate chips, 7 ounces marshmallow creme
Once combined, stir in the vanilla. The mixture will begin to harden as it cools so before it begins to set, quickly stir in the butterfinger candy bar pieces.
1 teaspoon pure vanilla extract, 1 cup chopped Butterfinger candy bars
Pour the fudge into the prepared pan and spread evenly with a rubber spatula. Sprinkle the top of the fudge with the remaining crushed Butterfinger candy bar (optional), and very gently press it into the top of the fudge.
¼ cup chopped Butterfinger candy bars
Cover the pan with plastic wrap and let the fudge cool in the refrigerator for a few hours, until the fudge is completely cooled and has set. Cut into 1-inch squares and serve.