01 - Combine water, lemon juice, and sugar in a small saucepan. Heat over medium-low, stirring continuously until the sugar fully dissolves. Remove from heat and let cool to room temperature before using.
02 - Add cold mascarpone, heavy cream, granulated sugar, lemon zest, lemon juice, and vanilla extract to a large mixing bowl. Beat with an electric mixer on medium-high speed until the mixture is smooth, thick, and holds soft peaks.
03 - Quickly dip each ladyfinger into the cooled lemon syrup — avoid soaking, just a brief pass on each side. Arrange a single layer of dipped biscuits across the bottom of an 8x8-inch dish.
04 - Spread half of the lemon cream evenly over the base layer of ladyfingers using a spatula, ensuring full coverage to the edges.
05 - Dip another batch of ladyfingers in the syrup using the same quick method and place them over the first cream layer.
06 - Spread the remaining lemon cream over the second biscuit layer and smooth the top surface evenly with a spatula.
07 - Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours, or overnight for the best texture and flavor development.
08 - 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 chilled.