Preheat oven to 275°F (135°C). Line two baking sheets with parchment paper or silicone baking mats. Set aside.

Combine the first 4 ingredients (the dry snacks!) in a large mixing bowl.

Place the remaining ingredients, except for the chili powder, in a medium saucepan over medium heat. Stir until the butter has melted. Pour over the dry ingredients and carefully stir to coat.

Spread evenly on prepared baking sheets and bake for 1 hour, stirring every 15 minutes. Remove from the oven, sprinkle with a little chili powder (for extra spice, if desired), then allow to cool completely on the baking sheets. The Chex mix will crisp up as it cools.

Cover tightly and store at room temperature for up to 2-3 weeks.