Chocolate Cheesecake

16 to 20 servings

For the crust:

7 ounces shelled pistachios (from about 1 pound in the shell), toasted (a) and finely chopped, plus extra for garnish (optional)

1/2 cup tightly packed light brown sugar

1/8 teaspoon ground cinnamon

4 ounces (1 stick) unsalted butter, melted

For the cake:

8 ounces bittersweet chocolate, chopped

26 ounces cream cheese, softened

1 1/4 cups plus 2 tablespoons sugar

1/8 teaspoon salt

4 large eggs

1 cup heavy cream

2 teaspoons vanilla extract

For the ganache topping:

4 ounce bittersweet chocolate, chopped

1/2 cup plus 2 tablespoons heavy cream

For the crust: Combine the toasted chopped pistachios, brown sugar, cinnamon and melted butter in a small bowl. Wrap a 9-inch cardboard cake circle with plastic wrap; if you do not have a cake circle, cut a circle from a piece of corrugated or stiff cardboard, using the bottom of a 9-inch springform pan as a guide. Carefully press the nut mixture onto the cake circle, making sure to cover it completely. Cover and refrigerate for at least 1 hour.

For the cake: Preheat the oven to 325 degrees. Encase the outside of a 9-inch round springform pan in aluminum foil and set aside. Have ready a large roasting pan and a kettle of just-boiled water.

In a small bowl, melt the chocolate gently over a double boiler. Set aside to cool slightly.

In the large bowl of an electric mixer on low speed, beat the cream cheese, sugar and salt until the mixture is creamy, scraping down the sides of the bowl several times. Add the eggs one at a time, incorporating after each addition. Add the cream and the vanilla extract. With the mixer running, still on low speed, gradually add the melted chocolate and mix until completely incorporated. Pour the batter into the springform pan and smooth the top of the cake with a spatula. Place the springform pan in the roasting pan. Transfer to the middle oven rack, and pour the boiled water into the roasting pan until it comes halfway up the side of the springform pan. Bake for 60 to 70 minutes, until the top is just set. The cake should jiggle slightly when the pan is poked with a fork. Remove the pan from the oven and place the cake on a wire rack until cool. Cover with aluminum foil and refrigerate overnight in the pan.

For the ganache topping: Place the chopped bittersweet chocolate in a small bowl. Set aside.

In a small saucepan over high heat, bring the cream to a boil, then pour it over the chopped chocolate in the bowl. Stir until the chocolate is completely melted and the mixture is smooth. Set aside.

To assemble: Remove the cake circle of pistachio crust and the cheesecake from the refrigerator, discarding the foil. Loosen the cheesecake by carefully running a warm, dry knife around the inside edge of the springform pan. Unhinge the sides of the pan and remove. With the springform pan bottom still under the cheesecake, invert the cake circle onto the top of the cheesecake. Undo the plastic wrap, remove the cake circle and carefully peel off the wrap while gently pressing the crust into the cheesecake. Place a serving plate or cardboard cake circle on top of the crust, then invert the cheesecake so that the springform bottom is on top. Remove the springform bottom from the cheesecake top. (Slide a knife under it, if necessary.) Pour the ganache on the cheesecake and spread to cover the top. Sprinkle with chopped pistachios, if desired.

Refrigerate for several hours or, better yet, overnight.