01 - In a small saucepan, combine water, lemon juice, and sugar. Heat over medium heat, stirring continuously, until the sugar fully dissolves. Remove from heat and let cool completely to room temperature.
02 - In a large mixing bowl, combine the cold mascarpone, heavy cream, sugar, lemon zest, lemon juice, and vanilla extract. Using an electric mixer or whisk, beat until smooth, thick, and holding soft peaks.
03 - Briefly dip each ladyfinger into the cooled lemon syrup, just a quick pass on each side—do not let them soak or they will become mushy.
04 - Arrange a single layer of dipped ladyfingers in the bottom of an 8x8-inch dish, breaking pieces as needed to fit snugly. Spread half of the lemon cream evenly over the biscuit layer using a spatula.
05 - Add a second layer of quickly dipped ladyfingers over the cream. Top with the remaining lemon cream, smoothing the surface into an even, clean finish.
06 - Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours, or overnight, to allow the layers to meld and the texture to set properly.
07 - Just before serving, finish with a dusting of fresh lemon zest and optional white chocolate curls or mint leaves. Serve directly from the dish while still chilled.