Start with a 9x13 inch baking dish. There's no need to grease it, as the buttery crust will prevent sticking.

In a medium bowl, combine your finely chopped pecans, melted butter, and granulated sugar. Mix them together with a fork until all the nut pieces are evenly coated in butter. The mixture should resemble wet sand. Pour this mixture into your baking dish. Use the back of a spoon or the bottom of a measuring cup to press it down firmly and evenly across the bottom of the pan. Place the pan in the refrigerator to chill for at least 30 minutes.

While the crust is chilling, in a large bowl, beat the softened cream cheese with an electric mixer until it's completely smooth and free of lumps. Gradually add the powdered sugar, mixing on low speed until it’s incorporated. In a separate bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the cream cheese mixture until it’s just combined. (If using thawed whipped topping instead, simply fold that in.) Carefully spread this cream cheese mixture over your chilled pecan crust, making sure to go all the way to the edges to create a seal.

In another bowl, whisk together the two packages of instant pistachio pudding mix and the three cups of cold milk. Whisk for about two minutes, or until the pudding starts to thicken. Let it sit for a minute or two to firm up just a bit more. Then, pour and spread this pistachio layer evenly over the cream cheese layer.

Gently spread the thawed whipped topping over the pistachio layer. Create some lovely swirls and peaks with your spatula for a pretty, homemade look. Sprinkle the remaining chopped pecans or mini chocolate chips over the top.

Cover the dish with plastic wrap or a lid and place it in the refrigerator for at least 6 hours, but overnight is even better. This chilling time is crucial for the layers to set and flavors to meld.