Preheat oven to 250 degrees Fahrenheit.Spread Chex cereals, Teddy Grahams and almonds in a single layer on an ungreased cookie sheet.Place butter in a small microwave safe bowl and microwave in thirty second intervals until fully melted.Whisk in the brown sugar, pumpkin pie spice and vanilla extract.Drizzle the mixture over your dry ingredients. Stir gently to coat evenly.Bake for one hour, stirring mixture every fifteen minutes.Remove from oven and allow to cool completely before adding the M&Ms.Store in an airtight container for up to two weeks.