Preheat oven to 350 degrees F. Grease an 9x13-inch baking pan and line with parchment paper, leaving two flaps hanging over the edges of the pan. Grease and flour the parchment paper. Set aside.
In a medium bowl whisk together flour, baking powder, and baking soda. Add both the white and brown sugar to the dry ingredients and stir. Set aside.
In a separate medium bowl whisk together melted butter, eggs, and vanilla extract. Then add the wet ingredients to the dry and stir to combine. The dough will be thick and glossy. Stir in 1 cup of coarsely chopped candy. Use your fingers to evenly press the dough into the pan. Top with the remaining chopped Halloween candy.
Bake for 27 to 30 minutes until golden brown and cooked through. Allow to cool for 15 minutes in the pan before slicing into bars. Store at room temperature for up to three days.
Recipe by About a Mom at https://www.aboutamom.com/diy-halloween-treat-bags/