In a large bowl, mix mascarpone cheese and sugar until smooth.
In another bowl, whip heavy cream until stiff peaks form.
Gently fold whipped cream into the mascarpone mixture until combined.
Mix limoncello, lemon zest, and lemon juice in a separate bowl.
Layer crumbled lemon sponge cake at the bottom of a serving dish.
Drizzle the limoncello mixture over the cake crumbs.
Spread a layer of the mascarpone mixture over the soaked cake.
Repeat layers until ingredients are used up, finishing with mascarpone on top.
Refrigerate for at least 4 hours before serving, then garnish with fresh berries, mint, and a dusting of powdered sugar.