Combine graham cracker crumbs, sugar and melted butter. Press on bottom and sides of a greased 10 inch springform pan. Combine pudding mix, sugar and milk in saucepan. Add chocolate. cook and stir over medium heat until mixture comes to a full boil. Remove from heat. Cover surface with waxed paper and set aside.
Beat cream cheese until fluffy. Beat in yolks, vanilla, salt and pudding. Beat egg whites until stiff. Fold in egg whites. Pour over crumbs in pan. Bake on lowest rack at 425° F for about 35 minutes or until center is set lightly when touched. Cool 4 hours. Spread top with sour cream.
Preheat the oven to 350° F. In a food processor, combine the cream cheese, sugar, salt and eggs; blend until smooth, scraping down the sides of the container as necessary. Add the sour cream (see note), lemon juice, bourbon, vanilla and butter and blend.
Pour the filling into the cookie-crumb shell and bake in the middle of the oven for 45 minutes. Turn off the oven, prop the oven door open slightly and allow the cake to rest in the oven for 1 hour. Cool on a rack and refrigerate for at least 8 hours.
If the container of the food processor is not large enough, add only 1 cup of sour cream. Pour about half the mixture into a mixing bowl; add the remaining 2 cups of sour cream to the processor and blend. Combine both batches in the mixing bowl and stir to blend.