Step 1: Make the Crust
Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius). Lightly grease a 9-by-13-inch baking dish with butter or cooking spray. In a medium mixing bowl, combine the flour, softened or melted butter, finely chopped pecans, and the pinch of salt. Stir and work the mixture together until it is thoroughly combined and holds together when pressed between your fingers. Transfer the mixture to the prepared baking dish and press it firmly and evenly across the entire bottom of the pan using your hands or the bottom of a flat measuring cup. The layer will be quite thin — approximately a quarter inch — which is exactly right. Place the pan in the preheated oven and bake for 15 to 20 minutes, until the edges are just beginning to turn lightly golden. Remove from the oven and allow to cool completely to room temperature before adding any subsequent layers. This cooling step is not optional — adding the cream cheese layer to a warm crust will cause it to melt and slide.
Step 2: Prepare the Cream Cheese Layer
In a large mixing bowl, combine the completely softened cream cheese and the powdered sugar. Using an electric hand mixer, beat the two together on medium speed until the mixture is completely smooth and uniform, with no lumps of cream cheese remaining. This step requires that your cream cheese be genuinely at room temperature — cold cream cheese will produce a lumpy layer no matter how long you beat it, so plan ahead and take it out of the refrigerator at least an hour before you plan to start. Once the cream cheese and powdered sugar are fully combined into a smooth mixture, add the thawed whipped topping and fold it in gently using a rubber spatula until everything is evenly incorporated. The finished mixture should be light, fluffy, and creamy. Spread this cream cheese layer evenly over the completely cooled crust using an offset spatula or the back of a spoon. Place the dish in the refrigerator or freezer for about 20 minutes to allow this layer to firm up slightly before adding the pudding on top.
Step 3: Make the Chocolate Pudding Layer
Pour the three cups of cold whole milk into a large bowl. Add both packets of instant pudding mix — the chocolate and the vanilla. Whisk the mixture vigorously for about two minutes until the pudding is smooth and begins to thicken. The combination of the two pudding flavors produces a more complex and satisfying chocolate pudding flavor than chocolate alone, though you can certainly use two boxes of chocolate pudding if you prefer a more intensely chocolatey result. Place the bowl in the refrigerator for five minutes to allow the pudding to set up to a spreadable consistency. This is important: instant pudding sets quickly, so work with some efficiency here. Remove the chilled dessert dish from the refrigerator, and carefully spoon or pour the pudding over the cream cheese layer. Use an offset spatula or the back of a large spoon to spread it into a completely even layer covering the entire surface of the cream cheese layer. Return the dish to the refrigerator and allow the pudding to set completely — about 20 to 30 minutes — before adding the final topping layer.
