In a medium bowl, add the melted butter, brown sugar, and white sugar and mix to combine them.
Add the room temperature egg and whisk to combine it into the bowl.
Add the flour, baking powder, baking soda, and apple pie spice. Fold them into the cookie dough, and when the flour is almost completely incorporated, add the roughly chopped caramel popcorn pieces. Fold to combine.
Using a large cookie scoop, scoop the dough into about 10 cookies onto a parchment lined baking tray. The dough will be pretty soft. Top each dough ball with extra pieces of caramel popcorn.
Place the baking tray in the fridge for 45 minutes to chill the dough.
Then preheat the oven to 350 degrees F/177 degrees C. Bake the cookies for 13 minutes. Remove the tray from the oven and sprinkle with flaky salt to finish. Allow to cool before enjoying!