In a medium saucepan, combine the raspberries, sugar, and water over medium heat. Cook for about 10 minutes, stirring gently until the raspberries break down and soften. Mix cornstarch with a bit of water in a small bowl, then stir this mixture into the raspberry sauce, allowing it to thicken—remove from heat and let it cool completely.

In a mixing bowl, whisk the egg yolks and sugar until pale and creamy. Place this bowl over a double boiler and whisk continuously for 5–7 minutes, until the mixture thickens and becomes fluffy. Remove from heat, and gently stir in the melted white chocolate, ensuring it’s well combined. Allow this custard to cool before using it in the semifreddo.

In a separate large bowl, whip the heavy cream until stiff peaks form, indicating it’s ready. Take a small portion of the whipped cream (about 2-3 tablespoons) and fold it into the cooled egg mixture to lighten it. Then, carefully fold the remaining whipped cream into the egg and chocolate mixture until everything is beautifully combined, creating a light and airy consistency.

Line a loaf pan with plastic wrap, leaving enough overhang to cover the top later. Begin layering by adding half of the crushed sweet biscuits at the bottom of the pan. Pour in half of the creamy mixture, followed by a layer of the cooled raspberry filling. Repeat with the remaining biscuits, cream, and finish with the last layer of biscuits on top.

Cover the assembled semifreddo tightly with the plastic wrap, ensuring no air can enter. Place the pan in the freezer and let it set for at least 4-5 hours, or ideally overnight, to allow the flavors to meld and the texture to firm up perfectly.

Once set, remove the semifreddo from the freezer and let it sit at room temperature for about 5-10 minutes, making it easier to slice. Carefully lift the dessert out of the pan using the overhanging plastic wrap. Cut into slices and serve beautifully decorated with fresh raspberries or a sprig of mint for that elegant touch.