Begin by lining your 9x9-inch baking pan with parchment paper, leaving some overhang for easy removal later.
In a double boiler, combine the bittersweet chocolate chips and evaporated milk. Stir gently until the chocolate is melted and smooth.
In a mixing bowl, combine the crushed vanilla wafers, crispy rice cereal, and powdered sugar. Stir until everything is well mixed.
Once the chocolate is melted, pour it into the bowl with the dry ingredients. Stir until everything is thoroughly coated in chocolate.
Gently fold in the miniature marshmallows, peanut butter chips, and chopped nuts of your choice. Be careful not to break the marshmallows too much.
Transfer the mixture to the prepared baking pan. Use a spatula to spread it evenly, pressing down gently to ensure it holds together.
Place the pan in the refrigerator for at least 2 hours, or until the fudge is firm enough to cut into bars.
Once set, use the parchment paper to lift the fudge out of the pan. Cut into squares or bars and enjoy your delightful creation!