Preheat the oven to 350°F and prepare a 9-inch springform pan.
To make the Graham cracker base, mix together the Graham cracker crumbs, granulated sugar, and melted butter until well combined. Press the mixture firmly into the bottom of the prepared pan.
Bake the crust for 10 minutes or until lightly golden. Set aside to cool while preparing the filling.
To make the filling, beat the softened cream cheese and granulated sugar together with an electric mixer until smooth and creamy. Add the eggs one at a time, mixing well after each addition. Mix in the heavy cream, Irish whiskey, and melted chocolate until well combined.
Pour the filling over the cooled crust and smooth the top with a spatula.
Bake the cheesecake for 45-50 minutes or until the edges are set and the center is slightly jiggly. Turn off the oven and leave the cheesecake in the oven with the door slightly ajar for 30 minutes to cool gradually.
Remove the cheesecake from the oven and allow it to cool completely. Cover the cheesecake with plastic wrap and refrigerate it for at least 4 hours or overnight.
To make the salted pistachio topping, chop the pistachios and mix them with the sea salt. Sprinkle the mixture over the chilled cheesecake and serve.