Begin by gathering a large mixing bowl and add the fried chow mein noodles. Toss in the mini marshmallows to create a delightful mixture that balances crunch and sweetness.

In a medium saucepan over low heat, gently melt the mini marshmallows until they are completely smooth, stirring frequently for about 5 minutes. Once melted, remove from heat and immediately pour the marshmallow mixture over the chow mein noodles. Stir well to combine.

Stir in the mini M&Ms and rainbow sprinkles into the warm mixture, folding them in gently to ensure they distribute evenly.

Prepare a greased 9x13-inch baking dish by lightly coating it with non-stick cooking spray or butter. Press the mixture firmly into the bottom of the dish.

Place the baking dish in the refrigerator and chill for at least 2 hours until the bars are set.

After the bars are fully set, melt your chocolate sauce in a microwave-safe bowl and drizzle generously over the chilled bars. Allow to harden for 15-20 minutes before slicing into squares.