In a medium saucepan, combine raspberries, sugar, and water over medium heat. Stir occasionally until thickened, approximately 10 minutes. Cool and strain.

In a large mixing bowl, whisk mascarpone cheese, heavy cream, and powdered sugar together with an electric mixer on medium speed for 3-5 minutes until soft peaks form.

Quickly dip the ladyfingers into the cooled raspberry syrup and layer them in an 8-inch square dish.

Spread half of the mascarpone filling over the ladyfingers and grate half of a white chocolate bar on top.

Add another layer of dipped ladyfingers, then spread the remaining mascarpone filling and grate the remaining white chocolate on top.

Cover with plastic wrap and refrigerate for at least 6 hours, preferably overnight.