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.
02 - Heat milk until steaming in a saucepan. Whisk egg yolks with sugar and cornstarch. Gradually pour hot milk into yolk mixture while whisking constantly. Return to pan and cook over medium heat, stirring, until thickened. Remove from heat, add vanilla, and cool completely.
03 - Combine mixed berries with sugar and lemon juice in a bowl. Let sit for 10 minutes to release natural juices.
04 - Beat heavy cream, powdered sugar, and vanilla until soft peaks form.
05 - Layer half the custard over cake, then spoon in half the berries. Add half the whipped cream. Repeat layers with remaining cake, custard, berries, and whipped cream.
06 - Decorate top with chocolate eggs, colored sprinkles, and fresh mint if desired. Refrigerate at least 2 hours before serving.