1. Make the Raspberry Syrup
- Simmer and Mash: Begin by placing raspberries and water in a medium saucepan over medium-high heat. Use a potato masher or fork to crush the berries, releasing their juices.
- Strain: Once simmered, pour the mixture through a fine-mesh strainer set over a measuring cup. Gently press the berry pulp with the back of a spoon to extract as much juice as possible.
- Reduce: Return the strained juice to the saucepan, add sugar and lemon juice, and simmer until slightly thickened, about 4–5 minutes. Chill completely before using.
Pro Tip: Ensure the syrup cools thoroughly before assembling to avoid melting the mascarpone filling.
2. Prepare the Mascarpone Filling
- Whip Cream: Using a stand mixer with a whisk attachment, whip the heavy cream until stiff peaks form. Transfer to a separate bowl.
- Mix Mascarpone: Replace the whisk with the paddle attachment. Beat mascarpone cheese, sugar, raspberry syrup, and vanilla until smooth and fluffy.
- Combine: Gently fold the whipped cream into the mascarpone mixture to create a light, mousse-like texture. Chill until ready to use.
3. Assemble the Tiramisu
- Soak Ladyfingers: Dip each ladyfinger in the cooled raspberry syrup, ensuring it’s soaked but not overly saturated. Arrange a single layer in an 8-inch square dish.
- Layer Filling: Spread half of the mascarpone filling over the ladyfingers, smoothing it with a spatula. Grate half of the white chocolate evenly over the layer.
- Repeat: Add another layer of syrup-soaked ladyfingers, followed by the remaining mascarpone filling. Pipe the top layer using a pastry bag for a decorative finish. Grate the remaining white chocolate over the top.
- Chill: Cover the dish with plastic wrap and refrigerate for at least 6 hours, preferably overnight, to allow the flavors to meld.