Make the crust: In a medium bowl, combine 2 cups graham cracker crumbs, 6 tablespoons melted butter, 3 tablespoons sugar, and 1/4 teaspoon salt. Stir until the mixture looks like wet sand, about 1–2 minutes. Checkpoint: The mixture should hold together when squeezed.

Press the crust firmly into a 9-inch pie dish, covering the bottom and sides evenly with your fingers or the bottom of a measuring cup, about 3–5 minutes. Checkpoint: The crust should be compact and level.

Refrigerate the crust for 15 minutes while you prepare the filling. This helps it set and prevents it from crumbling.

Prepare the avocados: Cut 3 ripe avocados in half lengthwise, remove the pit by pressing a knife into it and twisting, then scoop the soft flesh into a food processor bowl. Work quickly—avocados brown fast. Checkpoint: You should have about 1.5 cups of avocado flesh.

Immediately add 1/2 cup fresh lime juice to the food processor with the avocados. Pulse to combine, about 30 seconds. The lime juice prevents the avocado from turning brown.

Add 1 can (14 ounces) sweetened condensed milk, 8 ounces softened cream cheese (cut into small pieces), 1/4 cup sour cream, and 1 teaspoon vanilla extract to the processor. Blend on medium speed for 60–90 seconds, stopping to scrape down the sides halfway through. Checkpoint: The mixture should be completely smooth with no lumps of cream cheese visible.

Transfer the avocado mixture to a large bowl. Using a rubber spatula, gently fold in 1/4 teaspoon nutmeg and 1/8 teaspoon cayenne pepper by hand, about 20–30 seconds. Stir just until the spices are evenly distributed. Checkpoint: You should see no streaks of spice remaining.

In a separate, very clean bowl, pour 1 cup heavy whipping cream. Using an electric mixer on medium-high speed, whip the cream until soft peaks form (cream holds shape but tips curl over), about 2–3 minutes. Checkpoint: Lift the beaters—the cream should form peaks that gently fold over.

Add 2 tablespoons granulated sugar to the whipped cream and continue beating until stiff peaks form (cream stands straight up), about 1–2 minutes more. Do not overbeat or you will make butter. Checkpoint: Cream should be thick and glossy.

Fold 1/3 of the whipped cream into the avocado mixture using a rubber spatula, gently turning the bowl and cutting down the center, folding over, and rotating the bowl. Repeat this motion 15–20 times, about 1–2 minutes. Checkpoint: You should see some white streaks.

Add the remaining 2/3 of the whipped cream and fold gently until no white streaks remain and the filling is light and fluffy, about 2–3 minutes. Do not overmix or the filling will deflate. Checkpoint: The mixture should be pale green and airy.

Remove the crust from the refrigerator. Pour the avocado cream filling into the crust, filling it to about 1/2 inch from the rim. Use a spatula to smooth the top into an even layer, about 1–2 minutes. Checkpoint: The surface should be level and smooth.

Cover the pie loosely with plastic wrap and refrigerate for at least 4 hours, or preferably overnight (8–12 hours). The pie needs this time to set completely so it slices cleanly. Checkpoint: When you touch the filling lightly, it should feel firm and not jiggle.

About 15 minutes before serving, remove the pie from the refrigerator to bring it to a cool room temperature for easier slicing and better flavor.

Just before serving, dust the top of the pie evenly with 2 tablespoons powdered sugar using a fine-mesh sifter, about 30 seconds.

Garnish the top of the pie with fresh lime zest (using a microplane or fine grater), a few fresh cilantro leaves, and thin lime slices arranged decoratively. Do this just before serving so garnishes stay fresh and bright.

To slice the pie: Fill a tall glass with hot water. Dip a sharp chef's knife into the hot water, wipe it dry with a clean cloth, and make one smooth downward cut from the center to the edge. Repeat for each slice, dipping and drying the knife each time. This gives you clean, beautiful slices without smudging.

Serve immediately on chilled plates. The pie begins to soften quickly at room temperature.