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 milk in a saucepan until steaming. Whisk egg yolks with sugar and cornstarch until smooth. Gradually pour hot milk into yolk mixture while whisking constantly. Return mixture to pan and cook over medium heat, stirring continuously until thickened. Remove from heat, stir in vanilla extract, and 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 juices and flavors to develop.
04 - Whip heavy cream with powdered sugar and vanilla extract using electric mixer or whisk until soft peaks form. Do not overbeat.
05 - Layer half the custard over the sponge cake base, followed by half the macerated berries, then half the whipped cream. Repeat layers with remaining cake, custard, berries, and whipped cream, ending with whipped cream on top.
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.