To prepare pumpkin cheesecake, coat the inside of a 9"x1 1/2" cake pan with 1 tsp. Butter. Line the pan with an 8-inch square of parchment paper. Coat the parchment paper with the remaining teaspoon of butter. Set aside until needed.
Place 1 pound of softened cream cheese, 3/4 cup sugar, the flour, and 1/2 tsp. Salt in the bowl of electric mixer fitted with a paddle. Beat on low for 1 minute and on medium for 2 minutes. Scrape down sides of bowl, then beat on medium for 2 more minutes and on high for 3 minutes. Scrape down bowl. Add 3 eggs, one at a time, beating on high for 20 seconds and scraping down bowl after each addition. Add 1 tsp. Vanilla and beat on medium for 15 seconds, then beat on high for 2 more minutes. Add the pumpkin puree, cinnamon, allspice, and cloves, then beat on medium for 30 seconds. Remove the bowl from the mixer. Use a rubber spatula to finish mixing the batter until it is smooth and thoroughly combined. Pour the pumpkin cheesecake mixture into the prepared cake pan, spreading evenly.
Place a 9"x1 1/2" cake pan partially filled with 4 cups of hot water on the bottom rack of the 300 F oven (the bottom rack should be at least 3 inches below the center rack). Place both cheesecakes on the center rack of the oven and bake for 1 hour and 10 minutes, until the internal temperature of the cheesecake fillings reaches 170 degrees F. Turn off the oven and allow the cheesecakes to remain in the oven for an additional 20 minutes. Remove form the oven and cool at room temperature for 20 minutes. Refrigerate the chocolate cheesecake for 1 hour, but keep pumpkin cheesecake at room temperature (do not remove either cake from pan.
To prepare the ganache, heat the heavy cream, butter, and sugar in a 2 1/2-quart saucepan over medium-high heat. When hot, stir to dissolve sugar. Bring the mixture to a boil. Place the chocolate in a stainless steel bowl. Pour the boiling cream over the chocolate and allow to stand for 5 minutes. Stir until smooth. Allow to cool to room temperature.
Pour 1 cup of the semi-sweet chocolate ganache over the top of the chilled chocolate cheesecake. Spread evenly over the top of the cake. Invert the pumpkin cheesecake onto the layer of ganache. Gently press down on the cake to set in place. Wrap the entire springform pan with film wrap and refrigerate for 3 hours.
The cheesecake can now be released from the springform. Remove film wrap and wrap a damp, hot towel around the sides of the pan (the towel should be large enough to completely wrap around and cove the sides of the pan) and hold around the pan form 1 minute. Carefully release and remove the springform pan. Using a cake spatula, smooth the sides of the cake with 2 to 3 Tbsps. Of the ganache. Spread the remaining ganache evenly across the top of the cake. Press remaining cookie/pecan crumbs into the sides of the cake, coating evenly. Refrigerate for at least 30 minutes before cutting and serving.
Heat the blade of the serrated slicer under hot water before cutting and run it under hot water after making each slice.
(In the notes section of the recipe called The Chef's Touch, Marcel suggests the following: For an extra special touch, decorate the top of the uncut cake with sour cream and brown sugar: whisk together in a stainless steel bowl 3/4 cup sour cream and 1 Tbsps. Light brown sugar. Pour the mixture onto the center area of the cake. Using a spatula, spread the sour cream to within 2 inches of the outside edge of the top of the cake. Now for the final touch, evenly space 12 pecan halves 1/2 inch from the outer edge of the top. Refrigerate for an hour before cutting and serving.)