In a large mixing bowl, combine all crust ingredients and mix until well combined. Press the cookie mixture into the bottom and sides of a 10-inch tart pan. Bake the crust until fragrant, about 8 minutes. Allow to cool for at least 15 minutes before adding the filling.
To prepare the filling, place the cream cheese and sugar in a large metal bowl and, using an electric mixer, beat until creamy and smooth, about 4 minutes. Turn the mixer off and scrape the sides of the bowl with a rubber spatula. Continue mixing on low and add the egg; beat to incorporate. Scrape the sides of the bowl again. With the mixer still on low, pour in melted chocolate, and mix.
Pour the filling mixture over the cooled crust. If the mixture is too firm to settle, smooth the top of the filling with a few drops of water. Bake until the cake rises and puffs at the center, about 25 minutes. Remove fr om the oven and place on a wire rack to cool. Refrigerate at least 4 hours before proceeding.
To make the cream, combine powdered sugar and pistachios in a food processor. While the processor is running, slowly pour in heavy cream.
Within a few minutes the mixture will thicken. Spread the cream over the cheesecake.