Preheat oven to 160°C (325°F). Grease bottom and sides of 8-in. (20-cm) square baking pan (for best results, use a metal one).
Note: Use only the packaged brownie mix, not the added ingredients as called for on package. In medium bowl, whisk brownie mix with pumpkin pie spice. Stir in pumpkin puree and egg. Mix until smooth (batter will be thick). Spread evenly in prepared pan. Sprinkle on one or more choices of toppings, if using.
Bake until toothpick inserted in centre comes out with just a few moist crumbs on it, 34 to 37 min. Cool pan on wire rack. Cut brownies into squares to serve.