PREPARE THE CHOCOLATE TRUFFLE CAKE: Preheat the oven to 300 degrees Fahrenheit. Lightly coat the insides of a 9 by 3-inch springform pan with the melted butter. Set aside. Heat 1 inch of water in the bottom half of a double boiler over medium heat. Place 1-1/2 pounds semisweet chocolate and the remaining butter in the top half of the double boiler. Tightly cover the top with plastic wrap. Allow to heat for 15 minutes. Remove from the heat and stir until smooth. Transfer the chocolate to a 5-quart stainless steel bowl, using a rubber spatula to remove all the chocolate from the double boiler. Keep at room temperature until needed. Heat 1 inch of water in the bottom half of a double boiler over medium heat. Place 4 eggs and 4 egg yolks in the top half of the double boiler. Whisk the eggs until they reach a temperature of 110 degrees Fahrenheit, about 2 to 3 minutes. Transfer the heated eggs to the bowl of an electric mixer fitted with a balloon whip. Whisk on high until the eggs become light and pale in color, about 6 to 7 minute. Remove the bowl from the mixer. Using a rubber spatula, gently fold one third of the eggs into the melted chocolate. Add the remaining eggs and fold together gently, but thoroughly. Pour the batter into the prepared springform pan. Place the springform pan onto a baking sheet on the center rack in the preheated oven. Bake for 1 hour 10 minutes to 1 hour 15 minutes, until the internal temperature of the cake reaches 170 degrees Fahrenheit. Remove the truffle cake from the oven and allow to cool in the pan for 45 minutes. Before releasing the cake from the springform pan, use your fingertips to press down gently on the outside edges of the cake (to create as flat a surface as possible.) Remove the sides (but not the bottom) of the springform pan and refrigerate the cake until needed, for at least 1 hour.