In a microwave-safe bowl, warm the white chocolate chips, cookie butter, and butter for 30-seconds. Remove from microwave and stir until the mixture is completely mixed together. You may need another 20-30 seconds in the microwave to have it really melt together.
In a very large bowl, place the Chex cereal and cookie pieces. Pour the melted cookie butter mixture over the cereal and cookies, and using your hands, gently combine, ensuring all pieces are thoroughly coated.
Place the powdered sugar, cinnamon, and salt in a large Ziploc bag and whisk together. Pour the Chex and cookie mixture into the Ziploc bag, secure the top, and shake everything together until the powdered sugar is fully combined with the cereal.
Pour the mixture into a serving bowl or store at room temperature for 5-days.
Recipe by Her Modern Kitchen at https://www.hermodernkitchen.com/biscoff-cookie-butter-muddy-buddies/