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 the milk in a saucepan until steaming but not boiling. In a separate bowl, whisk together the egg yolks, sugar, and cornstarch until smooth and pale. Gradually pour the hot milk into the yolk mixture while whisking constantly to temper the eggs. Return the entire mixture to the saucepan and cook over medium heat, stirring continuously, until thickened to a pudding consistency. Remove from heat, stir in the vanilla extract, and allow to cool completely.
03 - Combine the mixed berries with sugar and lemon juice in a medium bowl. Toss gently to coat and let rest for 10 minutes to allow the berries to macerate and release their natural juices.
04 - Using an electric mixer or whisk, beat the heavy cream with powdered sugar and vanilla extract until soft peaks form. Be careful not to overwhip.
05 - Spread half of the cooled custard over the cake layer in the dish. Spoon half of the macerated berries evenly over the custard. Top with half of the whipped cream. Repeat the layers with the remaining cake, custard, berries, and whipped cream.
06 - Garnish the top with chocolate eggs, colored sprinkles, and fresh mint leaves as desired. Cover and refrigerate for at least 2 hours before serving to allow the flavors to meld and the layers to set.