01 - In a medium mixing bowl, combine the strawberries, blueberries, raspberries, and granulated sugar if using. Gently toss and set aside for 10 minutes to allow juices to develop.
02 - In a large bowl, whip the heavy cream using an electric mixer or whisk until soft peaks form. Add the softened mascarpone or cream cheese, granulated sugar, and vanilla extract. Continue whipping until the mixture is smooth and thick.
03 - If preparing homemade vanilla custard, cook according to your chosen method and let cool completely before use.
04 - Arrange half of the cubed pound cake or sponge cake in the bottom of a trifle dish or individual serving glasses.
05 - Spoon half of the macerated berries and their juices evenly over the cake layer.
06 - Spread half of the vanilla custard over the berries, followed by half of the vanilla cream mixture, smoothing each layer gently.
07 - Repeat layering with the remaining cake cubes, berries, custard, and vanilla cream to form distinct layers.
08 - Top with extra berries and fresh mint leaves if desired. Cover and refrigerate for at least 1 hour before serving to allow flavors to meld.