Preheat the oven to 350 degrees F. Spray a 12-cup (10 inch) Bundt pan with flour-added baking spray. If you are using a black Bundt pan, use 325 degrees F.Melt chocolate in a metal bowl set over a saucepan of barely simmering water (or just use the microwave). Scrape it into a mixing bowl and let cool slightly.
Whisk in the oil and sugar until smooth, then whisk in the egg and vanilla.
Mix the flour, cocoa powder, baking soda and salt together in another bowl.
Add half of the dry ingredients to the chocolate mixture along with 1/2 cup of the coffee and 1/2 cup of the buttermilk; whisk until smooth.
Add the remaining dry ingredients, coffee and buttermilk and whisk until smooth.
Pour the batter into the prepared pan and bake in the lower third of the oven for about 45 minutes, or until a toothpick inserted in the center of the cake comes out with a few moist crumbs attached.
Let the cake cool on a rack for 10 minutes, then turn it out and let cool completely.In a small saucepan, bring the cream to a boil. In a heatproof bowl, combine the remaining 3 ounces of chopped chocolate with the corn syrup and butter.
Pour the hot cream over the chocolate and let stand until melted, about 5 minutes.
Whisk until smooth.
Let the ganache glaze cool until thick but still pourable, about 5 minutes.
Pour the ganache over the cooled cake.
Let the cake stand until the glaze is set, at least 30 minutes, before serving.
