1. In a heavy saucepan, combine brown sugar, corn syrup, water, butter, and pumpkin pie spice.
2. Bring to a boil, stirring until sugar is dissolved.
3. Reducei heat and gently boil, stirring occasionally, until a candy thermometer reaches 285°F (syrup separates into hard, but not brittle, threads when dropped into very cold water).
4. Gradually pour over popcorn, tossing to coat evenly.
5. Spread out on a lightly buttered cookie sheet.
6. Cool and break into small pieces.