Lightly grease a 9×13-inch baking dish or spray it with nonstick spray. For clean slices, line the bottom with parchment paper, leaving some overhang to lift the dessert out later.

In a medium bowl, stir together the graham cracker crumbs, granulated sugar, melted butter, and a pinch of fine sea salt until evenly moistened and resembling wet sand.

Press the crumb mixture firmly into the bottom of the prepared pan, using the bottom of a measuring cup or glass to pack it down. For a no-bake crust, chill in the refrigerator for 20–30 minutes. For a firmer crust, bake at 350°F (175°C) for 8–10 minutes, then cool completely before adding the next layer.

In a mixing bowl, beat the softened cream cheese with an electric mixer until smooth and fluffy, 1–2 minutes. Add powdered sugar and vanilla extract and beat again until creamy, scraping down the sides as needed.

Gently fold 1 cup of the thawed whipped topping into the cream cheese mixture just until combined with no white streaks. Spread this cream cheese layer evenly over the cooled or chilled crust, going all the way to the edges to seal the crust.

In a large bowl, whisk together the instant pistachio pudding mixes and cold milk for about 2 minutes, until thickened and smooth. Let sit for 2–3 minutes more to finish thickening; it should be thick but spoonable, not runny.

Carefully spoon the pistachio pudding over the cream cheese layer in several dollops, then gently spread into an even layer using an offset spatula or the back of a spoon, taking care not to disturb the cream cheese layer underneath.

In a small bowl, fold the finely chopped pistachios into the remaining 2 cups of thawed whipped topping until evenly distributed.

Spread the pistachio whipped topping evenly over the pudding layer, going edge to edge.

Sprinkle the top with chopped roasted salted pistachios, extra graham cracker crumbs or crushed shortbread cookies, and, if desired, fresh berries and white chocolate shavings.

Cover the pan tightly with plastic wrap or a lid and refrigerate for at least 4 hours, or overnight, until the layers are fully set and the dessert is well chilled.

When ready to serve, run a knife around the edges. If lined, lift the dessert out using the parchment. Cut into bars with a sharp knife, wiping the blade between cuts for clean layers. Serve cold.