Step 1: Prepare all components. If making homemade lemon curd, ensure it's fully cooled and chilled until firm. Wash and gently dry the blueberries completely. If using pound cake, cut it into uniform 1-inch cubes. In a large, cold mixing bowl, whip the very cold heavy cream, powdered sugar, and vanilla extract until stiff peaks form. Set aside.
Step 2: Layer the first third of the cake cubes or ladyfingers evenly at the bottom of a large trifle bowl (approx. 3-quart capacity). Press them down gently to form a solid base.
Step 3: Gently spoon about 2/3 cup of the chilled lemon curd over the cake layer, spreading it as evenly as possible with the back of a spoon or an offset spatula. Avoid pressing too hard to keep the cake light.
Step 4: Sprinkle about 1.5 cups of fresh blueberries over the lemon curd layer. For an extra citrus kick, you can toss them with a tiny bit of lemon zest before adding.
Step 5: Spread approximately 1 cup of the prepared whipped cream over the blueberries, creating a smooth and even layer. Use a piping bag for a neater appearance if desired.
Step 6: Repeat layers: Add another third of the cake, followed by 2/3 cup of lemon curd, then another 1.5 cups of blueberries, and finally another 1 cup of whipped cream. Ensure each layer is distinct.
Step 7: For the final layer, place the remaining cake cubes evenly across the top, then spoon over the remaining lemon curd, and top generously with the remaining whipped cream. Smooth the top with a spatula or create decorative swirls.
Step 8: Garnish the top beautifully with the reserved fresh blueberries, additional lemon zest, and optionally a few thin lemon slices. Cover the trifle lightly with plastic wrap and refrigerate for at least 4 hours, or ideally overnight, to allow the flavors to meld and the cake to soften into a truly decadent dessert.