Pistachio pudding dessert

1/2 cup finely chopped pistachio or walnuts, divided
1/2 cup butter, softened
1 cup flour
1 tablespoon sugar
8 ounces cream cheese, softened
1 cup powdered sugar
1 liter Cool Whip topping, thawed, divided
2 packages Jell-O pistachio instant pudding, 4 servings each
2 1/2 cups cold milk

Heat oven to 325 degrees. Grease a 9-by-13 baking pan. Reserve 1 tablespoon nuts. Using a stand-up or hand-held mixer, combine the remaining nuts with butter, flour and sugar. Press flour mixture onto bottom of the prepared pan. Bake for 15 minutes and then set aside to cool completely. In a medium bowl, combine together cream cheese and icing sugar; whisk until well combined. Stir in 2 cups of Cool Whip. Spread cream cheese mixture over the cooled crust. Using a stand-up mixer, beat pudding mixes and milk with whisk on low speed for 3 minutes. Spread over cream cheese layer and let stand for 5 minutes or until thickened. Cover with the remaining Cool Whip. Refrigerate for 4 hours. Slice and sprinkle with remaining nuts just before serving.