Preheat oven to 300. Line 2 baking sheets with parchment, set aside.
Combine butter, pumpkin spice, salt, sugar and vanilla extract in a small pot and combine together until melted. Set aside.
Add all dry ingredients to a large mixing bowl, except the candy corn.
Pour butter mixture over chex mix and toss until well coated.
Split between two baking sheets in one layer. Bake on middle/top racks for 28 minutes, tossing half way.
Remove from oven and allow to cool completely before adding candy corn.
Store in an airtight container up to one week.