To make the compote, add the frozen berries, sugar, lime juice and elderflower cordial to a pan set over a medium heat, and leave it to simmer until it thickens into a jam-like texture.
Stir occasionally.
Remove it from the heat and allow it to cool down completely.
Use a hand mixer to beat the cream until it forms soft peaks, then add the cream to a piping bag fit with a large star nozzle.
To assemble the trifles, use dessert glasses, regular glasses or jars.
Dip a sponge in milk briefly and add it to the bottom of a glass.
Top it with a layer of compote, then a layer of custard and a layer of cream, then repeat with sponge, compote, custard.
For the final touch, pipe the cream and top with fresh mint leaves if you wish.
Repeat with the rest of the ingredients, I got 4 individual trifles.
Chill in the fridge for at least 2 hours before serving.