Cut your pound cake into 1 inch (ish) cubes. Set aside.
In a large bowl, beat together the instant pudding mix, milk, and 2 cups of the heavy cream for several minutes until it becomes thick and fluffy. Set aside.
In another large bowl, beat the remaining 2 cups of heavy cream with the powdered sugar until stiff peaks form. Set aside.
In your trifle dish, layer the ingredients, starting with a layer of pound cake cubes. Then add a layer of the pudding mixture, followed by a layer of the sliced strawberries and whole blackberries. Top that with a layer of whipped cream. Repeat the process until all the ingredients have been used- about 3-4 times.
Chill the trifle, and serve cold. Enjoy!