Preheat oven to 400 degrees F. Coat a large baking sheet with cooking spray.
Using the Halloween-themed cookie cutters, cut tortillas into fun shapes. Arrange tortillas on prepared baking sheet and spray with cooking spray. Season the tops with onion powder, salt and black pepper. Bake for 6 minutes, until crisp.
Meanwhile, in a large bowl, combine chicken, beets and scallions. Toss to combine, allowing beets to color chicken. In a small bowl, whisk together vinegar, oil and mustard. Pour mixture over chicken mixture and toss to combine. Season, to taste, with salt and black pepper.
Serve salad in lettuce leaves and top with goat cheese. Serve tortilla chips (ghouls) on the side.