Crush the cookies and mix with the melted butter. Grease an 7-inch (18 cm) springform pan and press the cookie mixture into the bottom and slightly up the sides to form a crust. Use a spoon to press firmly. Chill in the refrigerator for at least 30 minutes.

Meanwhile, make the panna cotta: Soak the gelatin sheets in cold water for 10 minutes. Heat the heavy cream with the chopped white chocolate, stirring until the chocolate is completely melted. Remove from heat, squeeze out the gelatin sheets, and add them to the warm cream mixture. Stir until dissolved. Let the mixture cool for about 20 minutes, then pour it into the cookie crust. Refrigerate for at least 4 hours.

Make the raspberry sauce: Rinse the raspberries and place them in a small saucepan with the sugar and lemon zest. Cook over medium heat for at least 3 minutes, stirring constantly. Let the sauce cool, then use some to decorate the cake, reserving a little to serve with the slices. Garnish with raspberries and mint leaves.