Prepare Raspberry Syrup: Combine raspberries and water in a medium saucepan, crush gently, and cook for about 5-7 minutes. Strain and return juice to the pan; stir in sugar and lemon juice, then simmer for 5 minutes. Cool completely.

Whip Cream: In a large bowl, beat heavy cream on medium-high speed for 2-3 minutes until stiff peaks form. Set aside.

Make Mascarpone Filling: In a stand mixer, combine mascarpone cheese, sugar, and cooled raspberry syrup. Mix on low until smooth. Gently fold in whipped cream.

Assemble Tiramisu: Dip ladyfingers quickly in raspberry syrup and layer half in an 8-inch square dish. Spread half of mascarpone filling, then sprinkle with 2 tablespoons white chocolate.

Repeat Layers: Add another layer of soaked ladyfingers, top with remaining mascarpone filling and garnish with extra white chocolate.

Chill: Cover with plastic wrap and refrigerate for at least 6 hours or overnight. Cut into squares to serve.