01 - Cube the sponge cake or ladyfingers into bite-sized pieces. Arrange half of the cake pieces in the base of a large trifle dish. Drizzle with orange juice or sherry if desired for added moisture and flavor.
02 - Heat whole milk in a saucepan until steaming but not boiling. In a separate bowl, whisk together egg yolks, granulated sugar, and cornstarch until smooth. Gradually pour the hot milk into the yolk mixture while whisking constantly to temper. Return the mixture to the saucepan and cook over medium heat, stirring continuously, until thickened. Remove from heat, stir in vanilla extract, and allow to cool completely.
03 - Combine mixed berries with granulated sugar and fresh lemon juice in a bowl. Toss gently to coat and let rest for 10 minutes to allow the berries to release their natural juices and intensify in flavor.
04 - Beat heavy cream with powdered sugar and vanilla extract using an electric mixer or whisk until soft peaks form. Be careful not to overwhip.
05 - Spread half of the cooled custard evenly over the cake layer. Spoon half of the macerated berries over the custard. Top with half of the whipped cream. Repeat the layers with remaining cake, custard, berries, and whipped cream.
06 - Garnish the top with chocolate eggs, colored sprinkles, and fresh mint leaves as desired. Refrigerate for at least 2 hours before serving to allow flavors to meld and layers to set.