In a clean bowl, whisk the egg whites, sugar, and lemon juice together until you achieve white fluffy peaks.
In a separate bowl, whisk the whipping cream until fluffy. Fold in the egg white mixture, a splash of limoncello, the lemon zest and carefully fold into the whipping cream.
In another bowl, combine 1 cup limoncello with water. Add more water (to dilute the limoncello) and sugar, if desired.
Lightly dip both sides of each lady finger cookie in the limoncello mixture. The exterior of the cookie should be wet while the interior should remain somewhat dry. Arrange the dipped cookies in one tightly packed layer on the bottom of a cake pan. Spread 1/2 of the cream mixture evenly over the cookies, making sure the cookies are completely covered. Add a second layer of dipped lady fingers, and then evenly spread the remaining cream mixture on top. Sprinkle the top with lemon zest and lemon-infused white chocolate.
NotesUnlike the traditional tiramisu, this version can be served immediately.