Position the oven to 350° F with a rack just below center.
In a medium bowl, mix the butter, graham cracker crumbs, and sugar until blended.
Press the mixture firmly and evenly over the bottom of an ungreased 9-inch spring form pan.
Set the pan on a baking sheet and bake the crust 12 to 15 minutes, until golden brown.
Set the pan and baking sheet on a rack to cool.
When cool enough to handle, grease the sides of the pan above the crust and set aside.
Reduce the oven temperature to 300 degrees.
Put the chocolate in a medium bowl.
Pour boiling water over the chocolate and shake the bowl to submerge the chocolate. Cover and let stand for 2 minutes without stirring.
Whisk the chocolate and water until thoroughly blended and smooth. Set aside.
In a large bowl, beat the cream cheese just until smooth, about 45 seconds,
Add the sugar, vanilla, and salt, and beat just until smooth (about 1 ½ minutes), scraping the bowl and beaters once or twice.
Beat the eggs in one at a time, just until blended.
Use a rubber spatula to stir the melted chocolate thoroughly into the filling.
Scrape the filling on top of the crust and spread it evenly.
Bake the cake, on the baking sheet, for 60 to 70 minutes, until edges of the cake are puffed but the center still jiggles like tender gelatin when the pan is gently shaken.
Set the pan on a rack. Slide a thin paring knife carefully around the upper edges of the cake to detach it from the pan, but do not remove the pan sides.
When the cake is cool, loosen the sides of the pan but do not remove them.
Refrigerate the cake until it is thoroughly cold, before covering it with plastic wrap.
For the best flavor, keep the cake refrigerated for at least 8 hours, preferably 24 to 36 hours before topping and serving
Puree half of the raspberries (2 2/3 cups) with the sugar in a blender or food processor.
Strain the puree through a medium mesh strainer to remove the seeds, stirring and pressing on the solids to extract as much puree as possible.
Measure puree and add water if necessary to make 1 cup.
Whisk the cornstarch into the puree in a small non-reactive saucepan.
Bring the mixture to a simmer over medium high heat, stirring constantly.
Simmer 1 1/2 to 2 minutes, stirring constantly, until the puree is thickened and brighter in color. Set aside.
Uncover and remove the sides of the cake pan. If the top of the cake is moist, blot it with a dry paper towel.
Scrape the hot topping on the cold cake and spread it evenly.
Refrigerate the cake for at least an hour to set the topping.
Arrange the remaining raspberries on top of the cake.
Formulation courtesy of Ghirardelli