01 - Preheat oven to 340°F. Line the bottom of a 9-inch springform pan with parchment paper and grease the sides thoroughly with butter.
02 - Combine crushed graham crackers, melted butter, chopped pistachios, and sugar in a mixing bowl. Press the mixture firmly into the base of the prepared pan, creating an even layer.
03 - Bake the crust for 10 minutes until lightly golden. Remove from oven and let cool completely while preparing the filling.
04 - In a large bowl, beat cream cheese and sugar with an electric mixer until completely smooth and fluffy, about 2-3 minutes.
05 - Mix in Greek yogurt (or sour cream) and vanilla extract until fully incorporated.
06 - Add eggs one at a time, mixing gently on low speed after each addition just until blended. Avoid overmixing to prevent air bubbles.
07 - Fold in ground pistachios and cornstarch until evenly distributed throughout the batter.
08 - Pour the filling over the cooled crust. Tap the pan gently on the counter several times to release any trapped air bubbles.
09 - Bake for 45 minutes or until the edges are set and the center has a slight jiggle when gently shaken.
10 - Turn off the oven, crack the door open slightly, and let the cheesecake cool inside for 1 hour to prevent cracking.
11 - Remove from oven and cool to room temperature, approximately 1 hour. Refrigerate for at least 4 hours or overnight until completely set.
12 - Whip heavy cream with powdered sugar until soft peaks form. Spread over the chilled cheesecake and sprinkle with chopped pistachios just before serving.