In a medium saucepan, combine fresh or frozen raspberries with sugar and water. Bring to a gentle simmer over medium heat for about 10-15 minutes, stirring occasionally, until the mixture thickens slightly. Once ready, remove from heat and let the raspberry syrup cool completely before using it to layer your White Chocolate Raspberry Tiramisu.

In a mixing bowl, whisk together mascarpone cheese and vanilla extract until smooth and creamy. In a separate bowl, whip the heavy cream until soft peaks form. Gently fold the whipped cream into the mascarpone mixture, creating a light and airy filling.

Prepare a 9x9-inch dish. Briefly dip each ladyfinger into the cooled raspberry syrup, ensuring they soak without becoming overly soggy. Begin layering by placing a single layer of soaked ladyfingers at the bottom, followed by a generous spread of the mascarpone filling. Repeat the layering process until all ingredients are used.

Cover the assembled tiramisu with plastic wrap or a lid, ensuring it's airtight. Refrigerate for at least 6 hours, although overnight is preferred for the best flavor.

Once chilled, remove the tiramisu from the refrigerator and carefully lift off the cover. For garnish, dust lightly with cocoa powder or decorate with fresh raspberries. Slice into squares and serve chilled.