Step 1: Prepare the Berries. In a medium bowl, gently combine the sliced strawberries with 1 tablespoon of granulated sugar and 1/2 tablespoon of fresh lemon juice. In a separate bowl, combine the blueberries with 1 tablespoon of granulated sugar and 1/2 tablespoon of fresh lemon juice. Let both berry mixtures sit for at least 15-20 minutes at room temperature to allow the juices to release.
Step 2: Make the Lemon Cream. In a large bowl, using an electric mixer, beat the softened cream cheese until smooth and creamy, about 2-3 minutes. Add the powdered sugar and beat until well combined, scraping down the sides of the bowl as needed. Beat in the fresh lemon zest and 2 tablespoons of fresh lemon juice.
Step 3: Whip the Heavy Cream. In a separate, chilled bowl, whip the heavy cream until soft peaks form. Gently fold the whipped cream into the cream cheese mixture until just combined and smooth. Be careful not to overmix.
Step 4: Prepare the Pound Cake. Cut the pound cake into 1-inch cubes.
Step 5: Assemble the Trifle. Choose a large, clear glass trifle bowl (approx. 3-quart capacity). Begin with a layer of pound cake cubes at the bottom, using about one-third of the total cake.
Step 6: Add a Layer of Blueberries. Spoon about half of the prepared blueberries over the pound cake layer, spreading them evenly.
Step 7: Add a Layer of Cream. Carefully spread about one-third of the lemon cream over the blueberries.
Step 8: Add a Layer of Pound Cake. Place another layer of pound cake cubes (one-third) over the cream.
Step 9: Add a Layer of Strawberries. Spoon about half of the prepared strawberries over this pound cake layer, spreading evenly.
Step 10: Repeat Layers. Add another layer of cream (another one-third). Then, top with the remaining pound cake cubes (the last one-third). Follow with the remaining blueberries and then the remaining strawberries. Finish with the last third of the lemon cream, spreading it smoothly over the top.
Step 11: Chill and Garnish. Cover the trifle loosely with plastic wrap and refrigerate for at least 4 hours, or preferably overnight. Before serving, garnish with fresh mint leaves or extra berries, if desired.