In a medium saucepan, combine raspberries and water over medium heat. Simmer for 10 minutes until berries soften and release juices. Strain to remove seeds, return juice to saucepan, stir in sugar and lemon juice, and simmer for an additional 5 minutes. Chill syrup.

In a large mixing bowl, pour heavy cream and beat until stiff peaks form, about 3-5 minutes. Set aside.

In a stand mixer bowl, combine mascarpone, granulated sugar, raspberry syrup, and vanilla extract. Mix until smooth. Fold whipped cream into mascarpone mixture gently.

Dip each ladyfinger into the chilled raspberry syrup and lay half in the bottom of an 8-inch square baking dish. Spread half of the mascarpone filling over ladyfingers and sprinkle with white chocolate.

Repeat layering with remaining ladyfingers, topping with remaining mascarpone mixture and additional white chocolate.

Cover with plastic wrap and refrigerate for at least 6 hours or overnight before serving.