In a heavy bottomed pot, combine the sugar and corn syrup and bring to a boil. Reduce the heat to low and cook for 5 minutes. Remove from the heat. Melt the 20 ounces chopped chocolate in the top of a double boiler over simmering water. Stir the chocolate occasionally as it melts. Remove the pan from the heat and stir in the butter. Set aside to cool slightly. With an electric mixer, beat the eggs at high speed until frothy. Lower the speed to medium and carefully pour the hot syrup into the beaten eggs. Add the melted chocolate and butter mixture and blend to a smooth consistency. Butter a 10 inch to 12inch round cake pan lightly and pour in the chocolate mixture. Set the cake pan into a larger pan (such as a roasting pan) and add hot water to rise halfway up the sides of the cake pan. Place in the preheated oven and bake about 45 to 50 minutes.
Being very careful not to scald yourself or get water into the torte, remove the pans from the oven, and remove the cake pan from the water bath. Cool the torte completely to room temperature before unmolding. Run a sharp knife around the inner circumference of the pan. Place a plate over the pan, invert, and, if necessary, tap the bottom of the pan with the knife handle to encourage the torte to release.
The torte should then be refrigerated for at least 3 hours before serving. While the torte is cooling, place the heavy cream in a thick bottomed pot and begin to heat gently. Add the remaining 8 ounces of chocolate, stir together while the chocolate begins to melt in the hot cream. Being careful not to burn, boil or scorch the chocolate, when the chocolate has melted almost entirely, remove from the heat and allow to cool for several minutes before pouring over the torte for a glossy "finish". Place the unmolded torte on a baking rack with a cookie sheet underneath, and pour slightly cooled chocolate ganache directly onto the center of the torte in one motion so that it will flow out in one smooth sheet over the top and sides of the torte. You can gently help this along with the aid of a spatula but is important to use still warmed ganache.
Allow to dry a few moments at room temperature. Then place the torte, baking rack, and cookie sheet into the refrigerator to chill completely and set firm. If you haven't overheated the chocolate or cream, this "ganache" will set and harden into a shiny "couverture" during the hour the torte is chilling in the refrigerator.