Preheat oven to 300°F. In a medium bowl, combine 1 cup flour, ½ cup softened butter, 1 cup chopped pecans, and pinch of salt until mixture is clumpy but holds together when pressed.
Press mixture evenly into bottom of 13x9-inch baking dish. Bake for 20-25 minutes until light golden brown. Remove from oven and cool crust completely before adding layers.
In a large bowl, beat 8 ounces softened cream cheese and 1 cup powdered sugar until smooth and creamy. Gently fold in 8 ounces whipped topping using a rubber spatula.
Spread cream cheese mixture evenly over cooled crust. If kitchen is warm, refrigerate for 10 minutes to firm up before adding pudding layer.
In another large bowl, beat 2 boxes instant chocolate pudding and 3 cups cold milk on medium speed for 2 minutes until combined and soft-set.
Carefully spread pudding mixture over cream cheese layer. Top with remaining 8 ounces whipped topping and sprinkle with ½ cup chopped pecans.
Refrigerate for at least 3 hours or overnight before serving. For clean slices, freeze 20-30 minutes before cutting, then use sharp knife dipped in hot water, wiping between cuts.