Preheat the oven to 350°F (175°C).
In a medium bowl, combine ½ Cup butter (softened), ½ Cup pecans (chopped), ½ Cup powdered sugar, and 1 Cup all-purpose flour until a shaggy dough forms. Press the mixture evenly into a 9×13-inch baking dish.
Bake the crust 15 minutes, until golden brown and fragrant. Remove from the oven and let the crust cool completely.
In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), beat 8 ounces cream cheese (softened) until smooth and fluffy. Add 1 Cup powdered sugar and 1 Teaspoon vanilla, and beat until combined.
Fold 8 ounces whipped topping into the cream cheese mixture by hand until fully incorporated. Spread this cheesecake layer evenly over the cooled crust. Refrigerate 10–15 minutes.
In a medium bowl, whisk together 2 (12 oz) cans evaporated milk and 2 (3.4 ounce) boxes instant pistachio pudding mix until the mixture is thick and smooth. Spread the pudding evenly over the chilled cream cheese layer. Refrigerate 10–15 minutes, until the pudding is set.
Evenly spread the remaining 8 ounces whipped topping over the set pudding layer. Sprinkle 1/4 Cup chopped shelled pistachios and 1/4 Cup chopped pecans over the top.
Chill the assembled dessert in the refrigerator for at least 3 hours before serving.