In a medium saucepan, combine fresh raspberries and water. Bring to a gentle simmer over medium heat, cooking for about 10 minutes until softened. Strain the syrup into a bowl, then stir in granulated sugar and lemon juice. Return to the saucepan, simmer for an additional 5 minutes, then chill in the refrigerator until cool.

In a large bowl, whip heavy cream until stiff peaks form, taking about 3-5 minutes. In a separate bowl, beat mascarpone cheese with 2 tablespoons of raspberry syrup until smooth. Gently fold whipped cream into the mascarpone mixture until fully combined.

Quickly dip each Savoiardi ladyfinger in the chilled raspberry syrup for just a second. Layer half of these dipped ladyfingers in a rectangular dish, creating a solid base. Spread half of the mascarpone filling over the ladyfingers, then sprinkle with grated white chocolate.

Repeat the dipping process with the remaining ladyfingers, placing them over the mascarpone layer. Pour the rest of the filling on top, smoothing it out. Finish by decorating with more grated white chocolate.

Cover with plastic wrap and refrigerate for at least 6 hours, ideally overnight, to allow the flavors to meld and the filling to set.