Combine lemon juice and granulated sugar in a small saucepan over low heat. Stir gently until the sugar dissolves and the mixture warms but does not boil.

Remove from heat and stir in 1/2 cup limoncello and the zest from 2 lemons. Taste for balance; it should be bright but smooth.

Let the syrup cool to room temperature. If you need it sooner, chill it briefly in the fridge, stirring once.

In a large bowl, whisk the mascarpone until it is smooth and free of lumps.

In a separate bowl, whip the heavy cream with 3/4 cup powdered sugar and 1 tsp vanilla extract until you see soft peaks.

Fold the whipped cream into the mascarpone in gentle strokes, adding a pinch of salt and 2 tbsp limoncello, until smooth.

Pour the cooled lemon-limoncello syrup into a shallow bowl. Dip each ladyfinger for just a second on both sides.

Arrange a single layer of soaked ladyfingers in the bottom of your 9×13 inch dish.

Spoon half the mascarpone cream over the ladyfingers and smooth gently.

Repeat with another layer of dipped ladyfingers and the remaining mascarpone cream. Smooth the top and sprinkle with additional lemon zest.

Cover the dish tightly with plastic wrap and place it in the refrigerator for at least 4 hours, preferably overnight.

Slice with a warm, clean knife and serve on small dessert plates with extra lemon zest and a mint leaf.