Start by lining your 9x9-inch baking pan with parchment paper, leaving some overhang on the sides for easy removal later.
In a microwave-safe bowl, combine the bittersweet chocolate chips and evaporated milk. Heat in the microwave in 30-second intervals, stirring after each interval until the mixture is smooth and fully melted.
In a large mixing bowl, combine the crushed vanilla wafers, crispy rice cereal, powdered sugar, and chopped nuts. Stir until evenly mixed.
Pour the melted chocolate mixture over the dry ingredients. Gently fold everything together until fully combined.
Carefully fold in the miniature marshmallows and peanut butter chips.
Transfer the fudge mixture into the prepared baking pan. Use a spatula to spread it out evenly.
Place the pan in the refrigerator for at least 2 hours or until the fudge is firm.
Once the fudge has set, lift it out of the pan using the parchment paper overhang. Slice it into squares.
