In a large bowl, prepare the vanilla pudding according to package instructions and set aside to chill for about 15 minutes.
In another bowl, whip the heavy cream, powdered sugar, and vanilla extract together until soft peaks form.
Gently fold the whipped cream into the chilled vanilla pudding until well combined.
In a large trifle dish or individual cups, layer half of the pound cake cubes at the bottom.
Add half of the sliced strawberries and half of the blueberries on top of the cake layer.
Spoon half of the pudding mixture over the fruit layer.
Repeat the layers with the remaining pound cake, strawberries, blueberries, and pudding mixture.
Top with whipped topping if desired and garnish with fresh mint leaves.
Chill the trifle in the refrigerator for at least 2 hours before serving to allow the flavors to meld.