Combine pecans, sugar and butter; mix well. Press on to the bottom of a 23 cm ( 23 cm ) spring form pan. Bake in 160ºC oven dozen min; set aside. Beat cream cheese until smooth. Beat in brown sugar, flour and vanilla until well blended. Add eggs one at a time, mixing well after each addition. Stir in chopped turtles. Pour on to pecan crust. Bake in 160ºC oven 10ºC 60 minutes, or until centre of cake is just set. Turn off oven and let cake stand in oven 30 minutes. Remove to a wire rack, cool to room temperature. Chill for at least 4 hours before service. Garnish with whole turtles. Makes 8-10 servings.