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 to add moisture and flavor.
02 - Heat whole milk in a saucepan until steaming. Whisk egg yolks with granulated sugar and cornstarch in a separate bowl. Gradually pour hot milk into the yolk mixture while whisking constantly. Return everything to the pan and cook over medium heat, stirring continuously until thickened. Remove from heat, stir in vanilla extract, and cool completely.
03 - Combine mixed berries with granulated sugar and lemon juice in a bowl. Let sit for 10 minutes to allow the berries to release their natural juices and create a sweet syrup.
04 - Using an electric mixer or whisk, beat heavy cream with powdered sugar and vanilla extract until soft peaks form. Be careful not to overwhip.
05 - Layer half the custard over the soaked cake base, then spoon in half the macerated berries with their juices. Add half the whipped cream. Repeat layers with remaining cake cubes, custard, berries, and whipped cream, ending with cream on top.
06 - Decorate the top with chocolate eggs, colored sprinkles, and fresh mint leaves if desired. Refrigerate for at least 2 hours to allow flavors to meld and the trifle to set before serving.