Preheat oven to 350°F. Line a cookie sheet with parchment paper. Melt the butter and allow it to cool. Chop the halloween candy and set aside.
In a medium bowl, add in flour, oats, cinnamon, cornstarch, baking powder, baking soda, and salt.
In a large bowl, whisk cooled butter, brown sugar, and white sugar. Add in egg and vanilla and whisk in.
Add in the dry ingredients and mix until a soft cookie dough forms. Don't over-mix!
Add in the leftover halloween candy and mix in a few times.
Scoop 6 cookie dough balls (about 1.5 tbsp per cookie) and place on the prepared cookie sheet.
Bake for 10-15 minutes. Mine took 13 minutes. The cookies will be ready when the edges are a golden brown, but the inside will look very soft. Remove from oven, let the cookies cool on the hot pan for a few minutes before serving warm or cool completely and enjoy!
