01 - Combine strawberries, blueberries, raspberries, and sugar in a medium bowl. Toss gently and set aside for 10 minutes to allow the berries to release their natural juices.
02 - In a large bowl, whip the heavy cream to soft peaks using an electric mixer or whisk. Add mascarpone cheese (or cream cheese), granulated sugar, and vanilla extract. Continue whipping until mixture is smooth, thick, and fully combined.
03 - If making custard from scratch, follow your preferred vanilla custard method and allow to cool completely before use.
04 - Arrange half of the cake cubes evenly in the bottom of a trifle bowl or individual serving glasses.
05 - Spoon half of the macerated berry mixture, along with their juices, over the cake cubes.
06 - Evenly spread half of the vanilla custard over the berries, followed by half of the prepared vanilla cream.
07 - Repeat the layering process with remaining cake cubes, berries, custard, and cream.
08 - Top with additional berries and fresh mint leaves if desired. Chill in the refrigerator for at least 1 hour to allow flavors to meld before serving.