In a big bowl, mix together the Corn Chex, Rice Chex, Crispix, pretzels, and pecans. Toss them gently to combine.

In a saucepan, melt the butter with brown sugar and salt over medium heat until it reaches a boil. Pour this mixture over the cereal and mix well to coat everything.

Spread the coated mix out on a rimmed baking sheet. Bake in an oven preheated to 250℉ for 10 minutes. After that, take it out and give it a good stir.

Return it to the oven and bake for another 45 minutes, stirring twice during cooking to ensure even crunchiness.

Allow the mix to cool completely before storing it in an airtight container. Enjoy your delicious creation!