Preheat oven to 350°F (175°C). Grease a 9-inch square glass baking pan.

In a large bowl, mix brownie mix, egg, 1/4 cup water, and vegetable oil until well-blended. Spread into prepared pan.

Bake for 25-30 minutes until a toothpick inserted near the edges comes out clean. Cool completely, then cut into 1-inch squares.

In another bowl, combine condensed milk, remaining 1/2 cup water, and pudding mix; mix until smooth. Fold in 8 ounces of whipped topping until no streaks remain.

In a trifle bowl, layer half of the brownies, half of the pudding mixture, and half of the 12-ounce whipped topping. Repeat layers. Shave chocolate on top for garnish.

Refrigerate for 8 hours before serving.