01 - Combine water, lemon juice, and sugar in a small saucepan. Heat while stirring until the sugar fully dissolves, then remove from heat and let cool completely.
02 - In a large mixing bowl, whisk the cold mascarpone, heavy cream, granulated sugar, lemon zest, lemon juice, and vanilla extract until smooth and thickened to a spreadable consistency.
03 - Briefly dip each ladyfinger into the cooled lemon syrup without soaking. Arrange a single layer of dipped ladyfingers across the bottom of an 8x8-inch dish.
04 - Spread half of the lemon cream evenly over the bottom layer of ladyfingers using a spatula.
05 - Dip a second batch of ladyfingers in the lemon syrup and arrange them over the first cream layer.
06 - Spread the remaining lemon cream over the second layer of ladyfingers, smoothing the surface into an even finish.
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 - Before serving, finish with a sprinkle of lemon zest and optional white chocolate curls or mint leaves. Serve chilled.