Press the crumbled amaretti firmly into the base of a 10cm/4in flan ring. Blend the peaches in a jug blender to a smooth puree. Whisk egg whites until soft peaks form. In a separate bowl, add the amaretto to the cream then whisk until stiff peaks form. Fold the peach puree into the amaretto cream. Gently fold the whisked egg whites into the peach mixture. Spoon the peach mixture over the amaretto base. Chill in the refrigerator for 2-3 hours or freeze for 2-3 hours. If frozen, remove from the freezer 20 minutes before serving to allow to thaw slightly. Decorate with peach slices and serve.