Preheat the oven to 300. Butter the bottom and sides of an 8" springform pan.
Put the semisweet chocolate in a medium bowl with the hot coffee. Let stand, stirring occasionally, until the chocolate is melted and the mixture is smooth and opaque.
Meanwhile, in another medium bowl, whisk together the sugar, flour, cocoa powder, baking soda, baking powder and salt.
In the bowl of a stand mixer beat the egg on medium speed until it is pale yellow, about 1 minute. Add the oil, sour cream, and vanilla, beating well. Gradually pour in the melted chocolate mixture, and beat to thoroughly combine. Add the dry ingredients all at once, and beat on low speed until the batter is just combined. Using a rubber spatula, scrape down the sides of the bowl and briefly stir to make sure that all the dry ingredients are absorbed. Do not over mix.
Pour the batter into the prepared springform pan. Place pan on a cookie sheet and bake for 55-60 minutes, or until a toothpick inserted in the center of one comes out clean. The sides of the cake will begin to pull away from the pan and the center of the cake should not dent when gently touched.
Transfer the cookie sheet with pan to a wire rack and cool for 10 minutes. Remove the cookie sheet and leave the cake in the pan, allowing it to cool completely.
To make the ganache, heat the heavy cream to a gentle boil and pour over the chocolate. Let sit for a minute or so to let the chocolate melt. Stir gently in a circular motion until smooth. Add the butter pieces and stir until smooth.
Pour the ganache onto the center of the cake allowing it to drip off the sides of the cake. If you have any left over ganache, use a spoon to drizzle it over slices when placed on a dessert plate.
Saturated fat: 5.2 g Unsaturated fat: 6.3 g Carbohydrates: 29 g Sugar: 19.8 g Fiber: 1.9 g Protein: 2.9 g Cholesterol: 29 mg