01 - Combine strawberries, blueberries, raspberries, and optional sugar in a medium bowl. Toss gently and allow to stand for 10 minutes to release juices.
02 - Whip heavy cream in a large mixing bowl until soft peaks form. Add mascarpone or cream cheese, sugar, and vanilla extract. Continue whipping until smooth and thick.
03 - If making custard from scratch, prepare according to your preferred method and cool completely before using.
04 - Arrange half of the cubed pound cake in the base of a trifle bowl or individual glasses.
05 - Spoon half of the macerated berries with their juices evenly over the cake layer.
06 - Spread half of the vanilla custard over the berries, then layer with half of the vanilla cream mixture.
07 - Repeat with the remaining cake, berries, custard, and cream to create a second layer.
08 - Top with extra fresh berries and mint leaves as desired.
09 - Refrigerate for at least 1 hour before serving to allow flavors to meld.