In a large bowl, combine chicken, potatoes, vegetables, soup, sour cream, milk, flour salt, pepper and garlic powder.
Transfer to a greased 9x13-inch baking dish.
Place the bread in a food processor, cover and process to make crumb; sprinkle over the chicken mixture.
Bake at 350 degrees for 40-45 minutes or until bubbly.
Meanwhile, on a lightly floured surface, unfold pastry sheet. Using a small, floured ghost-shaped cookie cutter, cut out 12 ghosts.
Place on an ungreased baking sheet.
Remove potpie from the oven; set aside and keep warm.
Bake ghosts at 400 degrees for 10 minutes or until puffy and golden brown.
Place on top of potpie; serve immediately.