**Prepare the Pudding:** In a mixing bowl, whisk together the chocolate pudding mix and cold milk until smooth. Let it set for 5 minutes.
**Cube the Brownies:** Cut the baked brownies into bite-sized cubes.
**Layer the Trifle:** In the trifle dish, start with a layer of brownie cubes. Add a layer of chocolate pudding, followed by a layer of whipped topping. Repeat the layers until the dish is full, ending with whipped topping.
**Add Toppings:** Sprinkle the top with chocolate chips, shavings, or chopped nuts if desired.
**Chill:** Refrigerate the trifle for at least 2 hours before serving to let the flavors meld together.