Set aside 1/2 cup of the raspberries to be used as garnish. Puree remaining 1 ½ cup of raspberries, then push through a sieve to get at least 6 tablespoons puree. In a small bowl, stir together 6 tablespoons of puree and 1 ½ teaspoons of sugar. In a second bowl, fold together a heaping 1/2 cup of whipped cream and 3 tablespoons of the puree to make raspberry whipped cream. Spoon about 2 rounded tablespoons of raspberry cream on top of a cookie. Top with a second cookie and continue sandwiching cream between cookies until you have a stack of 5 cookies with 4 layers of cream. Set stack on a plate, cover with plastic wrap, and freeze for about one hour. Keep remaining sweetened puree chilled. When cookie stack is are frozen, take off plastic wrap. Using a scraper or rubber spatula, spread remaining whipped cream over frozen stack, forming it into the shape of a small layer cake. Chill for 5-6 hours. When ready to serve, set Icebox cake on a serving plate, drizzle with remaining puree, and garnish with reserved fresh raspberries. Serves 2.