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.
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 to pan and cook over medium heat, stirring continuously until thickened. Remove from heat, stir in vanilla, and cool completely.
03 - Combine mixed berries with sugar and lemon juice in a bowl. Let stand for 10 minutes to allow berries to release their natural juices.
04 - Beat heavy cream with powdered sugar and vanilla extract until soft peaks form. Be careful not to over-whip.
05 - Spread half the custard over the cake base. Spoon half the macerated berries over custard, then add half the whipped cream. Repeat layers with remaining cake cubes, custard, berries, and whipped cream.
06 - Decorate 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.