01 - Preheat oven to 340°F. Line the bottom of a 9-inch springform pan with parchment paper and grease the sides.
02 - Mix crushed graham crackers, melted butter, chopped pistachios, and sugar in a bowl. Press the mixture into the base of the prepared pan. Bake for 10 minutes. Cool completely.
03 - In a large bowl, beat cream cheese and sugar until smooth and fluffy. Add yogurt or sour cream and vanilla extract, mix well.
04 - Add eggs one at a time, mixing gently after each addition until just combined.
05 - Stir in ground pistachios and cornstarch until fully incorporated and smooth.
06 - Pour the filling over the cooled crust. Tap the pan gently to release air bubbles. Bake for 45 minutes until edges are set and center still jiggles slightly.
07 - Turn off the oven, open the door slightly, and let the cheesecake cool inside for 1 hour.
08 - Cool to room temperature, then refrigerate for at least 4 hours or preferably overnight.
09 - Whip the heavy cream with powdered sugar to soft peaks. Spread over the chilled cheesecake and sprinkle with chopped pistachios before serving.