Step 1: Prepare the Raspberry Sauce

Cook the Raspberries: In a small saucepan, combine the raspberries, granulated sugar, and lemon juice. Cook over medium heat, stirring, until the raspberries break down and the mixture thickens (about 5 minutes).

Strain (Optional): Strain through a fine-mesh sieve if you prefer a smooth sauce. Set aside to cool.

Step 2: Make the White Chocolate Filling

Whip the Cream: In a mixing bowl, beat the heavy whipping cream and powdered sugar until stiff peaks form.

Combine with Mascarpone: In a separate bowl, whisk the mascarpone cheese and vanilla extract until smooth. Gradually mix in the melted white chocolate.

Fold in Whipped Cream: Gently fold the whipped cream into the mascarpone mixture until fully combined.

Step 3: Assemble the Tiramisu

Dip the Ladyfingers: Quickly dip each ladyfinger into the raspberry juice (or Chambord). Be careful not to soak them too long.

Layer: In a 9x9-inch dish, arrange a layer of soaked ladyfingers at the bottom. Spread half of the mascarpone-white chocolate mixture over them. Drizzle half of the raspberry sauce over the cream layer. Repeat with another layer of ladyfingers, mascarpone mixture, and raspberry sauce.

Step 4: Chill and Serve

Chill: Cover and refrigerate for at least 4 hours or overnight for best flavor.

Garnish: Before serving, top with white chocolate shavings, fresh raspberries, and a light dusting of powdered sugar if desired.