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. Whisk with an electric mixer on medium speed until the mixture becomes smooth, thick, and holds soft peaks.
03 - Working quickly, briefly dip each ladyfinger into the cooled lemon syrup. Do not soak — a quick one-second dip on each side is sufficient to soften without making the biscuits soggy.
04 - Arrange a single layer of dipped ladyfingers across 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 - Repeat with a second layer of quickly dipped ladyfingers, then top with the remaining lemon cream. Smooth the surface with a spatula to create an even finish.
06 - Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours. Overnight chilling yields the best texture and flavor integration.
07 - Just before serving, finish with a light dusting of fresh lemon zest and optional white chocolate curls or mint leaves. Serve directly from the dish while chilled.