In a large mixing bowl, whip the heavy cream until stiff peaks form. This can be done in a stand mixer with the whisk attachment at high speed for about 3 minutes, or using a hand mixer, or by whisking by hand (though this will take longer). The peaks should stand on their own when you lift the beaters out of the bowl. Refrigerate until ready to use, using 1 ¼ cups (300 ml) of cold heavy whipping cream.
In another large mixing bowl, beat the cream cheese and sugar together until light and fluffy, on medium-high speed for about 2 to 3 minutes, using 24 ounces (3 packages) of full-fat cream cheese and 1 cup (113 g) of confectioners' sugar.
Add the pistachio pudding mix, vanilla extract, almond extract, and sour cream, mixing on medium speed until smooth for about 1 minute, using 3.4 ounces (1 package) of instant pistachio pudding mix, 1 teaspoon of vanilla extract, 1 teaspoon of almond extract, and ¼ cup (57 g) of sour cream.
Gently fold in the whipped cream from the first step until no streaks remain.
Remove the crust from the freezer and spoon the cheesecake mixture into the prepared graham cracker crust, smoothing the top. Cover the springform pan with plastic wrap or tin foil (ensuring it doesn’t touch the top of the cheesecake) and refrigerate until firm, about 6-8 hours (preferably overnight for the best results).
When ready to serve, run a knife or metal spatula around the sides to loosen the edges of the crust from the springform pan, then remove the springform pan. Cut into slices and serve, ideally with homemade whipped cream and a sprinkle of chopped pistachios, using ¼ cup of chopped pistachios for garnish.