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 until steaming in a saucepan. 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 granulated sugar and lemon juice in a bowl. Let sit for 10 minutes to release natural juices and enhance sweetness.
04 - Beat heavy cream with powdered sugar and vanilla extract using electric mixer or whisk until soft peaks form. Do not overbeat.
05 - Spread half the custard over cake layer, followed by half the macerated berries. Add half the whipped cream. Repeat layers with remaining cake, custard, berries, and whipped cream, ending with cream on top.
06 - Decorate top with chocolate eggs, colored sprinkles, and fresh mint leaves if desired. Refrigerate for at least 2 hours to allow flavors to meld before serving.