01 - Cube the sponge cake or ladyfingers and arrange half in the base of a large trifle dish. Sprinkle with orange juice or sherry if using for added moisture and flavor.
02 - Heat whole milk in a saucepan until steaming. Whisk egg yolks with granulated sugar and cornstarch in a separate bowl until smooth. Gradually pour hot milk into the yolk mixture while whisking constantly to temper the eggs. Return everything to the pan and cook over medium heat, stirring continuously, until mixture thickens. Remove from heat, stir in vanilla extract, and allow to cool completely.
03 - Combine mixed berries with granulated sugar and lemon juice in a bowl. Let stand for 10 minutes to allow berries to release their natural juices and create a syrupy consistency.
04 - Using an electric mixer or whisk, beat heavy cream with powdered sugar and vanilla extract until soft peaks form. Be careful not to overbeat.
05 - Spread half the custard over the sponge cake base. Spoon half the macerated berries over the custard, followed by half the whipped cream. Repeat layers with remaining cake, custard, berries, and whipped cream, creating distinct visible layers.
06 - Decorate the top with chocolate eggs, colored sprinkles, and fresh mint leaves if desired. Refrigerate for at least 2 hours before serving to allow flavors to meld and layers to set.