Prepare the Pastry:

1. Add the flour, powdered sugar, and salt to the bowl of a food processor, and pulse until well combined. Add in the butter and pulse 5-7 times, or until the butter is broken down into tiny pebbles.
2. With the motor running, add in the egg and let the dough process until it forms together into a cohesive ball around the blade, about 1 minute.
3. Transfer the dough to a flour-dusted work surface.
4. Roll out the pie dough to an 11″ circle and line a 9” pie plate, crimp the edges as desired. Prick the bottom of the dough all over with a fork. Place the pie in the freezer while the oven preheats, at least 15 minutes.
5. Preheat the oven to 375ºF.
6. Once chilled, line the pie dough with a parchment round piece of paper and then add pie weights (or dry rice or beans or lentils), making sure to push pie weights to the edges.

Bake for 20 minutes, then remove from the oven and carefully remove the parchment and pie weights. Return to oven and bake for an additional 10 minutes, or until the pastry is fully cooked through. Set aside until ready to use.

Prepare the Pistachio Filling:

1. Add pistachios to a small food processor or high-speed blender (see note).
2. Process until the pistachios release their oil and are thick and creamy, scraping down the sides frequently, about 5-10 minutes. Pause this process as needed if your machine is getting too hot.
3. Add sugar, cornstarch and salt to a medium pot and whisk together. Whisk in the eggs, prepared pistachio butter and milk until fully combined. 
4. Heat the pot to medium and cook, whisking constantly, and occasionally taking a spatula and scraping up any thickened pudding in the edges of the pan. Cook until the pudding has completely thickened and large bubbles are forming and popping throughout and in the center, about 8 minutes.
5. Remove from heat; immediately pour through a fine mesh strainer into a clean bowl, using a spatula to push all the pudding out while leaving behind any bits of cooked egg or large pieces of pistachio.
6. Whisk in the butter and the almond extract into the pudding until fully combined.
7. Pour the pudding into the prepared pie crust and smooth over the top. Let cool at room temperature before chilling in the refrigerator for at least 3 hours or overnight.

Assemble the Pie:

1. Make the whipped cream: To the bowl of an electric mixer fitted with a whisk attachment, add cream cheese, sugar, and vanilla. Beat on medium speed, scraping down the sides of the bowl halfway through for 2 minutes. Add heavy cream and beat on medium speed until the cream has reached soft stiff peaks, about 2 minutes more.
2. Place whipped cream on top of the pie. Using an offset spatula spread the cream evenly on top of the pie. Garnish the pie with chopped pistachios.
3. Serve immediately or keep chilled until ready to serve, up to 1 day.