Preheat oven to 350ยบ. Grease a 9" x 9" pan with non-stick cooking spray.
In a mixing bowl, add softened butter and sugars. Beat until fluffy.
Add the eggs and vanilla to the sugar mixture and beat until combined.
In a medium bowl, add flour, baking soda, salt, and cinnamon.
Gradually beat in dry ingredients to wet ingredients.
Fold in chopped Halloween candy bars.
Spoon cookie dough into the bottom of the prepared pan and evenly spread it out.
Bake for 45 minutes or until edges of the cookie are golden brown and a toothpick comes out clean from the center.
Optional: while cookie bars are warm, press more chopped Halloween candy into the top of the cookie bars.
Allow bars to cool completely before cutting and serving.