Heat oven to 350 degrees F. Mix together pecans, flour and melted butter. Press evenly into a 9" x 13" baking pan or dish. Bake 20 minutes until lightly golden brown. Cool on wire rack to room temperature, then chill until ready to add cream cheese layer. Beat cream cheese with powdered sugar til well blended. Fold in 1 ½ cups of the whipped topping. Spread mixture onto cooled crust and refrigerate while preparing pudding filling. Combine chocolate and vanilla pudding mixes with cold milk in mixing bowl. Mix 2 minutes until well blended. Spread mixture evenly on top of cream cheese layer. Smooth enough of remaining whipped topping over top to make a layer about ½ inch thick. Refrigerate 4 hours or overnight before serving. Sprinkle servings with any of the optional toppings.