In a bowl, combine graham cracker crumbs, chopped pistachios, and sugar. Mix well.
Add melted butter and mix until well combined.
Press mixture onto the bottom of a 9-inch springform pan. Bake for 10 minutes, then remove from oven and let cool.
Meanwhile, using an electric mixer, beat cream cheese until smooth. Gradually beat in sugar and mix until well combined.
Beat in eggs, one at a time, then stir in vanilla extract. Pour mixture onto prepared crust.
Bake for 45-50 minutes or until the edges are set but the center still jiggles slightly. Let cool at room temperature for 1 hour, then refrigerate for at least 4 hours or overnight.
For the topping, heat heavy cream in a small saucepan over low heat until it comes to a simmer. Remove from heat and add chocolate chips and instant espresso powder. Stir until chocolate is melted and mixture is smooth.
Spread topping over cheesecake. Refrigerate for 30 minutes, then sprinkle chopped pistachios on top for garnish.
Serve chilled and enjoy your heavenly creamy mocha pistachio cheesecake!