Preheat the oven to 350°F, and position a rack in the lower third of the oven. Line a 6-inch round cake pan with parchment paper on the bottom, and lightly grease the sides with oil.

In a medium bowl, whisk together the flour, cocoa powder, and baking soda. Set aside.

In a small bowl, whisk together the oil, sugar, sour cream, egg, vanilla, and coffee. Combine the two bowls, mixing just until combined.

Pour the batter into the cake pan, and bake for 29-32 minutes, or until a toothpick inserted into the cake comes out clean. If under-baked, the cake will slightly sink.

Remove the cake from the pan, peel off the parchment, and place it on a small cake stand.

In a double boiler or microwave, melt the chopped chocolate, cream, and corn syrup (if using), stirring until smooth.

Pour the chocolate ganache over the cake, and garnish with pomegranate arils.