In a medium bowl, combine the graham cracker crumbs and melted butter until well mixed. The mixture should resemble wet sand.

Press the crumb mixture firmly into the bottom of a 9-inch springform pan. Use the bottom of a glass or your hand to get a nice, even layer. Place the crust in the refrigerator to chill while you prepare the filling, about 10 minutes.

In a large mixing bowl, using an electric mixer, beat the softened cream cheese and powdered sugar on medium speed until the mixture is smooth and lump-free, about 2-3 minutes. Make sure to scrape down the sides of the bowl as needed.

In a separate medium bowl, whisk together the instant pistachio pudding mix and cold whole milk for about 2 minutes, until the mixture begins to thicken. It will become quite green and fragrant!

Gently fold the thickened pudding mixture into the cream cheese mixture until just combined. Be careful not to overmix.

Add the thawed whipped topping to the pistachio-cream cheese mixture. Fold it in carefully with a spatula until no streaks remain and the filling is light and airy. Overmixing can deflate the topping, so be gentle.

Pour the luscious filling over the chilled graham cracker crust in the springform pan. Spread it out evenly using a spatula or the back of a spoon to create a smooth top.

Cover the springform pan loosely with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, until the cheesecake is completely firm and set. This is crucial for clean slices!

Once set, carefully remove the sides of the springform pan. Garnish the top of the cheesecake with chopped pistachios just before slicing and serving. Enjoy!