Prepare the Raspberry Syrup: In a medium saucepan over medium heat, combine raspberries and water. Crush the raspberries as they simmer for about 10 minutes. Strain into a bowl, mix in sugar and lemon juice, then simmer for another 5 minutes until thickened. Allow to cool completely.

Whip the Heavy Cream: In a mixing bowl, pour heavy cream and beat with an electric mixer on medium-high speed until stiff peaks form, about 3 to 5 minutes. Set aside.

Make the Mascarpone Filling: In a large bowl, blend mascarpone cheese with granulated sugar and cooled raspberry syrup until smooth. Fold in whipped cream gently until fully incorporated.

Assemble the Layers: Dip each ladyfinger into raspberry syrup for about 1 second on each side. Arrange in a single layer in an 8-inch dish. Spread half of the mascarpone filling over ladyfingers and sprinkle with half of the grated white chocolate.

Repeat and Finish: Add a second layer of soaked ladyfingers, topping with the remaining mascarpone filling. Garnish with remaining grated white chocolate.

Chill: Cover with plastic wrap and refrigerate for at least 6 hours, or overnight. Serve chilled.