Spray a 9x13-inch baking sheet with non-stick spray, or line with parchment paper.
Place chow mein noodles in a large bowl.
Heat butter in a large saucepan over medium heat and cook until just browned, then stir in marshmallows.
Use a rubber spatula and stir until melted and smooth, then pour mixture over chow mein noodles.
Optional (to make more gooey): heat ¼ cup butter and white chocolate chips in a medium saucepan over medium heat and stir until melted and smooth. Stir into chow mein mixture.
Transfer noodle mixture to greased or lined baking dish and press into an even layer.
Top with a drizzle of chocolate fudge, rainbow sprinkles and marshmallow bits.
Let set until firm, then slice into squares.
Recipe by Cooking TV Recipes at https://cookingtv-channel.com/buddy-the-elf-cookie-bars/