Prepare the Raspberry Syrup: In a medium saucepan, combine raspberries, water, and sugar. Bring to a boil over medium heat, stirring occasionally. Reduce the heat and simmer for 10 minutes, mashing the raspberries to release their juices. Strain the mixture through a fine mesh sieve into a bowl, discarding the seeds. Stir in the lemon juice and let the syrup cool completely.

Make the Mascarpone Filling: In a large mixing bowl, whip the heavy cream to soft peaks. Set aside. In another bowl, beat the mascarpone cheese, sugar, raspberry syrup, and vanilla extract until smooth and well combined. Gently fold the whipped cream into the mascarpone mixture to create a light, fluffy filling.

Assemble the Tiramisu: Dip each ladyfinger briefly into the cooled raspberry syrup, ensuring they are coated but not soggy. Arrange a single layer of syrup-dipped ladyfingers in the bottom of a 9x9-inch dish or similar serving dish. Spread half of the mascarpone filling evenly over the ladyfingers. Repeat the layers with the remaining ladyfingers and mascarpone filling.

Decorate with White Chocolate : Grate or shave the white chocolate over the top layer of mascarpone filling to garnish.

Chill and Serve: Cover the tiramisu with plastic wrap and refrigerate for at least 4 hours or overnight to allow the flavors to meld. Serve chilled, slicing into squares or scooping into dessert dishes.