In a medium saucepan, combine fresh raspberries, sugar, and water over medium heat. Cook for 10 minutes until the raspberries break down and the mixture is bubbling. Stir in cornstarch dissolved in a little water and cook for another 2-3 minutes until thickened and glossy. Remove from heat and let it cool completely to room temperature.

Using a mixing bowl, whisk together egg yolks and sugar until light and fluffy, about 5 minutes. Set the bowl over a double boiler and warm gently, stirring constantly for 5-7 minutes until pale and thick. Once done, remove from heat and stir in melted white chocolate until smooth. Let this mixture cool while you prepare the cream.

In a separate chilled bowl, whip the heavy cream to stiff peaks using an electric mixer, which should take about 3-5 minutes. Once whipped, fold a quarter of the whipped cream into the cooled egg and chocolate mixture gently to lighten it. Then, carefully fold in the remaining whipped cream to maintain airiness.

Line a loaf pan with plastic wrap, letting it overhang the sides for easy removal. Begin by adding a layer of crushed sweet biscuits at the bottom. Pour half of the cream mixture over the biscuits, smoothing it out gently before adding the raspberry filling in an even layer. Top with the remaining cream mixture, smoothing the surface again, followed by another layer of crushed biscuits.

Cover the assembled semifreddo with the overhanging plastic wrap and place it in the freezer. Allow it to chill for 4-5 hours or overnight until completely firm.

When ready to serve, remove the semifreddo from the freezer and lift it out of the pan using the plastic wrap. Let it sit at room temperature for 5-10 minutes to soften slightly for easier slicing. Cut into thick slabs and serve with extra raspberries and white chocolate drizzles for an elegant touch.