In a medium bowl, combine the sliced strawberries and blueberries. Set aside.
In another bowl, whisk together the vanilla pudding mix and milk until smooth. Let it sit for about 5 minutes to thicken.
In a large trifle dish or individual cups, layer half of the pound cake cubes at the bottom.
Spoon half of the pudding mixture over the cake, followed by half of the mixed berries.
Add half of the whipped topping, spreading it evenly over the berries.
Repeat the layers with the remaining pound cake, pudding, berries, and whipped topping.
Finish with a few whole strawberries and blueberries on top for decoration. Garnish with fresh mint leaves if desired.
Chill in the refrigerator for at least 1 hour before serving to allow the flavors to meld.